Lies we tell ourselves about email addresses
gitpush--force.com
gitpush--force.com
Once upon a time (1970/80s) I lived on and off in a mystic land called West Germany. Our postal addresses ended with incantations such as BFPO 40.
Around 1985ish my granny send a Christmas card to us. I should note that she was at this time nearly seventy and sadly suffering from Parkinsons. She addressed the card, in rather crabbed but legible handwriting, to:
Graham and Heath BFPO 40
My mum's name is abbreviated - her daughter. At that time Rheindahlen (nr Moenchengladbach) had a pretty large contingent of Brits in it - it was HQ (BAOR).
The card arrived well before Chrimbo and it took about a week judging by the post mark, which was petty normal in those days. She shoved it into a post box in Ipplepen, nr Newton Abbot, Devon and it found its way to an obscure address in another country. I seem to recall she also forgot the stamp but it still got through.
I'm sure mail like that becomes a point of honour to deliver and HM PO and BFPO did the job admirably.
That attitude is how email MTAs are generally designed to work. They cling on to the good old days and sadly the world is a bit shit. Case sensitivity ... lol!
I have some cousins who live in a small town in Australia where the houses have neither names nor numbers. You just address the envelope to ‘<name>, <street>, <town>’, and it’s the postie’s responsibility to know where everyone lives. (‘Postie’ is the official job title in Australia Post because it’s gender-neutral.)
https://www.mjt.me.uk/posts/falsehoods-programmers-believe-a...
Some time roughly mid-nineties we got numbers but originally they were just for emergency services, only later were they also for post, but I seem to recall the whole rural delivery system may have changed somehow around then too.
(I am a Brit and a massive fan of Footrot Flats)
Thankfully though, the postal worker knew my grandparents had grandchildren and therefore just asked the potential recipients for the name of their grandchildren to determine, which grandparents the postcard was addressed to. To me it's still a miracle that it got delivered at all.
Aside from regexes though, I also think the new TLDs confuse quite a lot of people. name@clientname.healthcare just doesn't click as an email address as quickly as name@clientname.com, and I'm in tech so I'm sure it's much more confusing for people outside that space.
In fact, that reminds me that we built a site for another client for use inside an exhibition space which was spacename.house and against our advice they put that - without www or https:// - on exhibition panels for use on mobile phones. I am absolutely convinced that most people didn't realise it was a web address.
having a 10 digits tld is self-harming
So if people just remembers spacename.house then that might be enough.
My dad tend to skip the TLD part as well. The results usually work. When they do not - he gets very confused.
The Internet is really a gold rush for scammers.
For years I've had a catch-all subdomain to give out addresses like company@sub.domain.tld which makes filtering out the junk when companies invariably sell their email lists or get hacked much easier. It is getting rarer, but I still occasionally run into sign-on forms that don't allow more than one “.” after the @ unless it is due to a recognised two-part country suffix like .co.uk.
I would never use something that isn't a country TLD for email for this reason, I assume there are a lot of bad systems out there that will incorrectly see them as incorrect.
This is one of my favorite articles on validating emails using RegEx, I fondly remember reading it over 15 years ago. It's stuck with me ever since.
Although more recently I’ve moved to a catch all domain for throwaway, which is even better. It confuses agents on the phone though when I give my email address as {their company name}@mydomain.com
Yeah, most people don’t understand how the ownership and control varies before and after the @ symbol.
People are still doing that? To prevent spam? To "catch" the company leaking/selling your address? Now the spammers know they can likely use anything@domain, and it'll get to your eyeballs in some capacity. Also, companies have no shame anymore, they don't care if you know.
If you want to 'self host' on a provider, I thing cheap/free options are available from cloudflare, Google, and similar enterprise companies.
If you want to truly self host, I don't have experience, but this guy who does gave a great thorough answer for those who are interested: https://news.ycombinator.com/item?id=48073510
I’m not concerned about the leaking as my address is out there anyway and Bayesian spam filtering is still decent enough, but as an aside, I have had two companies this year whose user databases must have been leaked on the basis of spam received at company-specific addresses. I reported it to their privacy people and pointed out it’s highly unlikely this “spam” originated as their (tiny company name) being chosen by chance by a spammer who figured out my catch all domain.
They never replied, and I probably should have followed up with the local information regulatory commission in each case. Hopefully, my note helped them identify they had a leak and to secure their systems.
Rather than whitelisting simply on a given sender, you can rely on both the sender and the recipient address matching a known list. This needn't be a single sender address. If you have multiple contacts at a domain, or a given entity relies on several email services (e.g., direct personal email, vendor-based marketing emails, vendor-based support or notification services), you could add all of these to the "from" match set.
I'm thinking through phone comms presently and am considering a similar concept for mitigating ever-growing phone abuse. Running a VOIP/PBX system, having multiple internal, non-public "extensions", each of which is valid for only a small subset of caller numbers. The "extension" space could be large (6--9 digits, say, millons to billions of values), making exhaustive search / coincidental match infeasible.
(This is only one of a few approaches I'm thinking of, it happens to resemble the specific email practice being discussed.)
And they sent me an email explaining how grateful I should be, that I'm grandfathered in to being able to use my own domain on a "plan" they dont even offer., in a plan that didn't offer custom domains.
Well how'd I get all that then? I signed up for fastmail explicitly because $5/yr for custom domains.
Anyhow if you pay a host you're probably fine. Or find someone with an old /24 thats had a /31 or /32 unused for a long while, and no other black marks against the /24. And use that IP, set up demarc and all the other new email DNS stuff.
The ticket began with a question about whether they'd be willing to change the way their WebDAV server handles query strings (by just ignoring them—versus returning 404, as it was doing at the time). The CEO subtly reframed the conversation as if I was accusing them of not following the standards. I wasn't. Git utterly screwed up how it does content negotiation. The change on their end would have made it easier to upload content into the file storage/web hosting space included with all plans[1] using git instead of a dedicated, conventional WebDAV client or the flaky support built into nautilus. I explained that I had originally planned to write a blog post about another one of the benefits of a Fastmail account, but the smugness and passive aggression of Bron's subsequent response—"Oh good. We don't want that," and his likening the use of git to push your static site to Fastmail's web hosting as akin to abusing DNS to tunnel arbitrary IPv4 data (wat)—and the general intellectual dishonesty I'd run into over the years seeing them respond to criticism e.g. here on HN, along with the fact that my plan was up for renewal in a month made the choice not to renew (and to try to dissuade others from giving their money to jerks) an easy one.
I switched to a different provider the next month, ended up saving money, and have only ever been met with warmth and kindness in the interactions I've had since switching, which is now going on 10 years ago.
1. <https://www.fastmail.help/hc/en-us/articles/360060590933-How...>
I do run similar infrastructure professionally for a living, which probably helps with getting it right first time. Competent VPS hosts care about IP reputation for mail; e.g. Hetzner only allows outbound port 25 for “trusted” customers, which somewhat helps with abuse reports. Some hosting providers may even let you relay via their own outbound hosts if you have a VPS with them, which simplifies the operational aspect.
I rarely need to send from the catch all address, but Postfix can easily be configured to allow my user to send from other addresses, and then it’s just a case of adding as an alias in your mail user agent.
I was worried about not being able to send emails, but is seems that as long as you setup properly SPF/DKIM/DMARC you're fine. You may have problems if using a domestic address though.
For the configuration, the best bet is probably to use a product that makes it easy to configure the above three, there are a few alternatives around, like Stalwart [1] or docker-mailserver (which is little more that your postfix/dovecot/rspam combo packaged in a container) [2]
I got everything setup correctly, but Microsoft seems insistent on silently dropping my email.
It gives me the fuzzies every time to explain I own the domain, and every email address on it is mine.
Since I have it on my phone, I can usually receive the email that they send very quickly and prove that everything's working fine.
I am wondering how hard it is to do this again today with a new domain though.
I was torn between explaining and letting them believe it :-)
Most of the time, folks just don’t understand why their company name is in the address and they think it’s a mistake.
To be honest, I do tend to avoid this for anything other than throwaways because it causes too much confusion when I have to phone up, and I’m not really doing it out of a misguided belief it helps with spam (at least, it doesn’t help any more than security by obscurity is unsuitable as a singular defence, but maybe has a tiny role when layered into a broader strategy…)
then if you start getting spammed, you use the w3w style thing to reverse it and see what site/entity sold your email...
then all of the "this doesn't/won't work because they'll just spam the entire domain" arguments go away, the "no, your email address" style comments go away...
you'd need an app or a mnemonic device of some sort if you wanted to give an email out in public as opposed to sitting at a computer. but ideally on the computer when you notice spam you just reverse the email address back to who you gave it to; "target.com", "kroger.com"
(with the last part being your own domain of course)
from.{their company name}@mydomain.com
from.{their company name}.{some numbers}@mydomain.comYou'd think big companies would know better than enlisting spammers to spam on their behalf, but I'm pretty sure Netflix had a scheme like this a few years ago. "Grow at any costs" sites like streaming or social media are probably happy with a tiny bit of plausible deniability for their spamming.
> I mean, I get it.
I don't.
Seriously, that's a huge fricking red flag. Obviously, most of those companies I would never do business with anyway, but this puts it over the line for all the others.
If they don't understand the first thing about validating their putative customers' emails by, you know, sending an email saying "is this really you?" then they've completely proven their technical incompetence.
The worst one is robinhood. I have two different email addresses that different people have used to sign up for robinhood accounts (back when they were giving anybody an account).
Occasionally, I tweak them about sending me shit.
"Sure! Just send us a copy of your photo ID to prove you're not that person."
Nah, bro, you've proven you're clueless, and there's no way I'm sending PIA to clueless people.
I wish this was asserted with evidence. The author might suggest this because they have unrealistic views of some users.
> In the year of our lord 2026, you can reasonably expect your users to know how to type their own email address - or even better, auto-input from their OS, browser, keyboard app, or password manager.
This really depends on who your users are.
I have multiple family members who have healthy memory, but can't accurately remember their email address everytime: the localpart, the domain, the syntax, everything.
Sending an email verification isn't sufficient, because if the user has typo'd ".com", they might never receive that email, and the user might never be back, or then have to escalate to support.
Meanwhile, if a site is opinionated on TLDs, they might prevent those users facing issues.
I'm sure there are many sites were users have a large variety of odd email addresses, but also there are sites that cater to mostly non-technical users within 1-2 locales, and so may find the friendliest UX is having opinionated validation.
But it is still lots more complicated than copying some imperfect email address regex, and for many sites, it's unlikely to even be worth spending much more effort than that.
Realistically, many sites can defacto choose to accept email addresses of few patterns. If a user's email address happens to be rejected, then they are either a non-technical user who quickly learns that they need a more commonly accepted email address, or a techie, who keeps a backup email address for these cases, and rightfully holds a grudge.
Most sites just aren't going to care enough to do anything more complex, for annoyed techies.
See also, IPv6 support.
And yes, I get annoyed if a site doesn't accept my domain-under-a-less-common-tld, or doesn't support IPv6. :)
> If an empty list of MXs is returned, the address is treated as if it was associated with an implicit MX RR, with a preference of 0, pointing to that host.
I don't know if most MTAs allow this though.
I got Gmail early enough that I have (my first name) dot (my last name) at gmail dot com. About twenty years ago, I started getting strange emails. At first I thought they were spam, because they were addressed to me by name but I had never joined those sites. Eventually I figured out that they were addressed to (my first name) (my last name) at gmail dot com. Which Gmail treats as the same address as the one with a dot in between.
Since I had never ever given out a version of my email address without a dot in the middle, I eventually figured out that these emails were meant for someone else who shared the same first and last name as me. But since I don't think Gmail would allow one person to register john.example@gmail.com and then later allow someone else to register johnexample@gmail.com, my name doppelganger must have registered firstnamelastname@yahoo.com, and then forgot the domain and given out firstnamelastname@gmail.com when asked for an email address. And probably never noticed that they weren't receiving emails like "Dear customer, thank you for purchasing (product). Would you like to try (other product)?", so they never realized that they were giving out the wrong email address.
And of course, also automated signup mails, newsletters (which I make sure to block and report as spam, unsubscribing is a feature for newsletters that are opt-in), transactional mails etc.
People really suck at knowing what their e-mail is. The private mails are down to 1/month, the others to ~3/week, but it used to be much higher for both categories.
Oh and of course there is some kind of weird scam going on where spammers on German classifieds (Kleinanzeigen) send an e-mail to firstlast@gmail.com for whatever public first and last name of the lister is, and ask if the product is still available. No link, nothing. And all sent via gmail which has by an overwhelming majority become the biggest sender of spam for me. I guess they are trying to get someone to reply and then do some manual scam or something.
Alternative explanation: A hastily scribbled "@ymail.com" (along with its relative infrequency) can look to many people like "@gmail.com".
Reading these dot-related comments reminded me that I once made one here about how I was able to leverage this possibly asynchronous dot-handling at gmail. Because the story is a bittersweet sentimental one for me I had to go back and read it now, and though I am sitting here with bad allergies streaming down my face, it also felt really nice to remember that.
I know this is a bit of a sideways comment, and I apologize for that but it isn't often I am overcome with emotion on HN, or on the topic of email addressing, and well, I appreciated the opportunity to re-read it now. Thanks.
You might find my gmail dots story interesting too. It's a little long, but the dot-character portion begins about a third of the way down in my comment:
https://news.ycombinator.com/item?id=46539424#46541149
Cheers!
If the user gets the email and completes the validation, the email is valid. If they fucked up, they don't get the email and the account never gets created.
No one ever gets prevented from creating an account with a legitimate email address, as opposed to "opinionated validation" where that absolutely will happen. Speaking from years of experience having a .info domain which isn't even all that odd, and at one point using gmail-style + addresses regularly. "Opinionated validation" has forced me to use my .com domain without a plus dozens of times.
I know part of this is intentional, those who know they plan to sell your email addresses don't want you to use the plus addresses, but that doesn't make the advice to not filter addresses any less correct.
"Did you mean layer8@gmail.com instead of layer8@gmailc0m [Y][N]".
But you can't do anything about that except asking them to validate their address with an email.
If you can catch 50% of user errors with some complex regex, but the other 50% such errors are uncaught, is that of any benefit during sofware design? No, because you still have to solve that problem, probably with email validation by code. You have reduced your workload by 0%, you just split it into 2 parts (unnecessarily).
In your example, the benefit is that users recover from the error 50% of the time at the time of registration, so it doesn't interrupt their workflow. Further, the fallback case (of contacting support, or enacting email validation, if a site chooses to implement) will see a dropoff in successful onboarding.
Of course, even then in the mid 90ies, UUCP was not something one really encountered outside of "so you think you're going to parse an email address with regexp?!" articles.
IBM Memo, Novel Netware etc. groupware and such X.400 and routing those required also odd email conventions. VAX VMS addresses did have % left side routing in too.
Ah well.
Where there is still room for improvement is in how email addresses are often made a little bit anonymous by a lot of websites. Did you ever see something like 'j*h@gmail.com'? Oh wow, that neatly leaves out John Smith's full name! Like showing only the last four numbers of an IBAN or credit card.
Except for us edge cases with a personal domain, where I then get 'm*l@myfullname.nl'. So stop that. Store it next to the bit of knowledge about validating email addresses — the bits of knowledge you use to correct junior developers and senior idiots.
The first sentence is that there is no single regex that perfectly validates every technically valid email address. I think that is a good start.
It then recommends the regex used for <input type="email"> and explains that this would cover the majority of email addresses used by actual people. It also shows an improved regex that handles dot-atom local parts, quoted strings, domain names, and IPv4 domain literals, but doesn't cover things such as comments, full IPv6 literals, or internationalized addresses.
It ends with the only correct advice (in my optionion): Send a confirmation email.
Claude Sonnet says:
> A practical email regex that covers the vast majority of real-world addresses: > > ^[a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,}$
Which is still way more complex than needed (and takes effort to read), and buggy according to years of blog posts written about this topic.
Of course the problem is the developer asking for a regex at all, but the must-regex-email instinct seems heavily engrained in our collective psyche.
I have no idea what other pay-to-play models say.
Maybe for some internal usages. but imagine someone from a country using different language and characters gives me a card with their email. It's now far less portable for me to use it. Those days, I surely could picture it and find the email most likely getting it right.
But email as means of international communication, like passport, should be readable as possible or it kills its purpose.
Even with ASCII emails I have, I already sometimes struggle to pass them over phone or other methods :)
So if it was broadly used and what charset used by a reasonable amount of the population then yeah I’d of course learn it in early age as I had to learn English.
It would be more portable for use with their peers who speak the same language, rather than requiring that everyone they want to communicate with in their own language and alphabet understands a second alphabet just for the addressing scheme.
\.{1,100}@\.{1,100}
I just don't like the idea of allowing to paste 20 MiB-long text into the input field for what normally is a "short line of text", so there should be some upper limit.
Even if they magically all switched to starting at DNS/TCP, that is still only 64KiB less header and EDNS0 and whatnot. And in that case one also has to allow space for sending the actual resource record set back in the response, DNS/TCP not having DNS/UDP's luxury of truncation, so it's not even as large as that.
To simplify implementations, the total number of octets that represent a
domain name (i.e., the sum of all label octets and label lengths) is
limited to 255.
You shouldn't be going through extra effort to get things wrong. Just use the thing that you're supposed to use.
mailbox@[x.x.x.x] and mailbox@[ipv6:...] (and probably without "ipv6" prefix once ipv4 is gone).
This is stronger than SPF since the second the IP of the sending SMTP server does not match the IP in the "from" headers and the envelope, the email is dropped, not even going into spam.
For instance, currently, if I send an email to a gmail slave, their parsers will ask for... a DNS PTR record, Oo "Geniuses" at work, or conveniently breaking all interop with small tech?
And the lie "users always read emails on the same device they're logging into a website with"
And the lie "users can always view HTML email so no need to send a plaintext equivalent, especially if I have a long complex URL I want them to click"
And the lie "Clickable links sent in email are more secure than passwords so I'll stop supporting passwords and instead rely on email delivery of a link for all logins. Whoever clicks that link first is definitely the user who wanted to log in"
God, I fucking hate that.
I have a fucking password manager, I have various machines and things open. Just let me fucking log in.
If anyone is reading this who is in charge of the internet please stop doing this.
My reasoning was this: my customers keep forgetting their password and somehow that becomes a trigger to contact me. No passwords, no problem.
I tried convincing them to use password managers but that was pointless.
But I see the pain and frustration so I will add passwords. And I quite liked the passkey idea, have to see how that works. Not that my customers would ever use it, but I would. It literally never occured to me.
It’s wild that they’re like “it’s more secure to not have a password” and then choose two unencrypted delivery mechanisms for the very short OTP.
Sure, people who reuse passwords are not secure. And fair, I guess it’s a tragedy of the commons. But at least continue supporting it and make it dead simple for password managers if you actually care bout security
OTP can be used with a password.
Passkey is still inferior to U2F + password anyways.
1. Enter username (e.g. an email)
2. Choose from either email or SMS on file
3. Enter the code you got somehow through the respective unencrypted channel
Given that this same site is involved with bank-account details for payment, I am concerned...
Yeah — loose the phone and it’s pretty much game over.
Time-code apps or passkeys are a different story.
1. You should be able to make backups.
2. There's nothing to intercept in plaintext.
3. The all can (unlike SMS features) be locked down by default and require a second layer of unlocking, so that they usually aren't accessible to someone who grabs your phone out of your hand.
I have many ways to generate totp codes. All of them are vastly more convenient than sending me an email or sms
Most other providers I've used range from instant to a few minutes.
Or the same browser, or the same browser-profile. For example, on my phone I have external links (from other apps) opening in incognito mode by default.
Larger customers have IT staff and set up OIDC or SAML with us. We don’t add an SSO tax.
The Big Problem™ however is case sensitivity in the local-part, because there multiple incompatible things collide:
1. Users are not universally aware of case (in)sensitivity in one direction or the other
2. Existing systems may or may not interpret case at all
My preferred solution would be to adjust the standard to ignore case in the local part by forcing it to lowercase. That aligns with most of the systems and mental model of technically proficient users anyways. It makes much more sense from an UX standpoint since the goal is to be imambiguous.
If we were to enforce the opposite: case sensitivity in the local part this would have multiple downsides:
1. It is inconsistent with itself by making the local part case sensitive but the host part not, that is harder to explain
2. You have to train users to be precise about case on entry. As someone who worked in IT-support, this is a very bad idea. This includes second-order issues like phishing attacks by silbling emails where just the case differs
3. If your service stores email addresses it will need to know whether that specific Mailserver/client/etc treats the email as case-sensitive or not
In my eyes email servers that allow case sensitive local-parts are functionally broken, even if they don't break any rules.
- what case you use to send mails
- what rules you use to determine if two email strings are the same user
For the first you can and should always use the address exactly as entered. For the second that's going to be a guess anyway and the exact rules depend on what false positives and false negatives mean for your use case - and you are going to have at least one of those two. Assuming case insensitivity here is generally reasonable for most use cases.
I registered a ".consulting" domain for my little company when they became available, and it has proved highly problematic ever since. Strangely (or perhaps not) it seems to be the larger players that have the most problems. I would at lest have expected ISPs and comms companies to keep up with this (looking at you, Three)
It was also a bloody nuisance. Spam filters were one thing but there were so many validation forms that failed.
Every reasonable variation of the company name as a .com/.net/.org was taken, including <companyname>company.com
Ugh, what a nightmare.
Domain holders are the landed gentry of tomorrow if we keep this up.
Even then it seems better to come up with a different prefix, or suffix (or both!), just to stay with ‘.com’.
Of course hindsight is 20/20 and I did the same, my personal homepage used to have a ‘.xyz’ address.
That also means that customers WILL confuse your company with others in non-domain contexts so perhaps it's a good idea to choose a more unique company name.
E.g. to simplify code, or if they wanted all mails to have a domain (if, for example, they wanted to integrate with reputation systems that were domain oriented)?
To your question, yes any product decision is possible, but enterprise/government people are surprisingly demanding about this stuff working because they have extremely weird requirements for routing mail to and through legacy systems. So I bet this still works at the mailer level and is broken in the UI.
Interesting context, thanks.
I'm trusting this is a throwaway example and that you used a real IPv6 address literal in this test, without the "IPv6" and with only colons and no dots (unless you mean to use v4 mapped address with dots)? Because this IPv6 literal is so malformed that I'm hardly expecting it to do something sane and changing that to "@2001" is nasal-demons quality undefined behavior. I tried with this exact literal and it let me send it but then there was a tiny red pop-up at the top of the gmail interface that said "could not be delivered, check your network connection" (which is odd; the same kind of pop-up that appears in gray when you legitimately are not connected to the internet) and it ended up in my drafts with the To: field empty.
I just tried to send a message to a "test@[" my current IPv6 address "]", and gmail told me
Error
The address "test@[«redacted»]" in the "To" field was not recognized.
Please make sure that all addresses are properly formed.
A lot of small business owners use gmail or a longstanding ISP account. A lot of people have personal email addresses you can’t easily distinguish from professional ones, between college alumni addresses, personal domains, and obscure ISP and email providers that aren’t in your database.
@hosta.int,@jkl.org:userc@d.bar.org
Compared to sending a mail or to a customer not getting a mail they wanted?
> Try to keep it as non-restrictive as possible. Something like ^[^@]+@[^@\s]+$, which only makes sure your user has input “something@something”
Requiring a dot in the domain part is perfectly valid. It makes no sense to not validate that the address is in a format that you can actually send something to, which include a domain that you can look up and isn't specifically rejected by your MTA.
> This belief will probably be more commonly held in the English-speaking world, but I’m curious: If you’re not in the Anglosphere, do you still expect emails to require ASCII latin characters?
Yes, I do not trust Unicode with all its ambiguities and alternate forms to resolve to the same identifier on your and that I intended. ASCII-only email addresses are the norm everywhere I have seen.
yeah, that is a pretty bizarre claim, as if millions of accounts are created per second
frankly this claim makes me think this article is LLM generated, because while the claim is technically correct, it's not a real concern
Don't just put a link into your mail that directly verifies an email when visited. At least put some button or code input field there.
Why? There are mail clients that will automatically open links for users and if that link is now invalid the user is confused about being able to click them.
The token was recently used? No problem! Must be a duplicate click, or a refresh, or the user left the browser tab open and their mobile device refreshed when they reopened the browser app, etc.
Is correct, you can have quoted local parts and (I guess?) theoretically "foo"@mail and foo@mail should even be treated the same.
But practically this is a dead feature and probably should be treated as non existing.
AFIK `[<ip-address]` mails are used by some old data centers for delivering automatic generated "error" mails from unix server in a way which doesn't break when DNS is down.
Also interestingly the `[..]` syntax has a generic extension hook, and that hook allows usage of @ characters. So technically a `foo@[custom:@@@@@@@@]` is a valid mail address, just no one knows how to deliver it ;). (And `custom` must be registered with IANA, theoretically).
through the message does allow an additional display name (like `display name <email>`) which has it's own rules.
the funny part is this is only half true
The true part: Punycode has never be standardized for the localpart and as such taking a email address with non us-ascii characters in the local part and punycode encoding it is fundamentally wrong.
But: Nothing prevents you to have a local part which "happens" to look like punycode and especially in the early SMTPUTF8 days many providers which did allow non-us-ascii email local parts automatically created an "alias" email address where the local part was punycode encoded. Nothing in the standard prevents this and as consequence punycode encoding a local part _might_ just happen to work for some subset of non-us-ascii emails.
The worst is some foreign gambling site, I can't even log into to change the preferences and cancel the account.
Though, I did deface then delete someone's dating profile once, who signed up on an app with my email...
Next is the spicy take: I need to consider WHY I am gathering this email?
If I'm gathering it for "marketing purposes" or any such cross correlation to other systems, then I'd also reject bob.smith+dontspamme@gmail.com. Or I'd keep both so you can do cross referencing on both the + address and the "raw" one.
For robust systems the goal was never to allow user type any technically valid email. It is to allow only emails that will not cause issues in the future.
Anyone who also enjoyed it would probably get a kick out of my article on the same subject that goes into the regex (which has some valid use cases): https://hackernoon.com/on-the-practicality-of-regex-for-emai...
The what now? I'm struggling to take this seriously because a decade ago regex where common knowledge, like if you don't have a handle on this you should probably go get a job in marketing levels of common knowledge. Has the profession fallen off this far in ten years?
Yes, it has fallen off this far in the last ten years.
If you look a little further back, say to 2006-ish it's far worse than that.
Back then there were 'bright' middle-school ROV team members writing C and Ada+Spark for Arduino-board control-by-wire small craft to perform simulated ocean sample collection and tool manipulation tasks and winning in the unlimited class against university competition at international championships.
Now the "Profession" consists of teams using ChatGPT to cheat on basic coding tasks and "make nudify" of famous people from their work machines.
> But the real reason I do that is just because I just like to sit in anger whenever this breaks the user experience because of programming errors or inconsistencies.
Genuinely delighted by the fact that I’m not alone in that.
I appreciate your commitment to correctness but like [XKCD 1172](https://xkcd.com/1172/) ... the user is clearly in the wrong at this point.
But if used as a senders source address there are even less limits.
For example you can use a null address <> when sending. That has been used bit less these days than earlier. It's been used ages SMTP delivery status notifications, mail loop prevention and so where intentionally not much sense to expect anyone to reply. And all well known MTA's forward it and email clients handle it very well by disabling reply to that message.
There is however a catch that anyone who thinks he would now start using it when he doesn't want any reply. Ever since IT Service Management (ITSM) and Service Desk software appeared, they have had issues with email coming from <> sender, because they like to always add received messages email addresses to database, where then someone handling would reply. I've been using only few, Service Now (SN) more lately and before Issue Tracker (IT), both didn't at least about year and half ago know how to handle null sender addresses. Both seemed to just discard or sort some trash bin those emails. With our SN sysadmin didn't find where those went in that system.
But otherwise <> as a sender works great. And sure it would be great if those ITSM making folks would get this fixed, because when your postmaster, postmaster, etc. and such role-aliases are the quite often handled by ITSM software, there is good chance you don't get some important notifications from systems that rely on that null address sender.
ps. Search Google: smtp and sender address as "<>" for more info incase needed.
Functionally there's no false positives or false negatives
Lies we tell ourselves about users.
I think this is mostly common with Gmail-heavy countries and does not apply to Europe? At least I do not know of anyone that thinks so.
pretty bad advice, if taken only as written, without adding more flavor on top.
the major email providers will penalize you if you generate too many undeliverable emails. thus, if you just send a verification email without any pre-validation, it's pretty easy to get into a DoS situation where current/valid users don't get important email sent to them, or that email is significantly delayed, plus incur huge operating cost to resolve the problem.
some form of rate limiting is needed, plus IMHO it's better to use a verifier service or your own heuristic or ML model to test for email validity including valid but fake/spammy/disposable addresses.
sorry, but we are way past the point of being able to have nice things, esp. when we're talking about email.
the "lies" part of the content is great. people do assume all those wrong things. however the TLDR is just wrong, and potentially harmful.
What pre-validation could you do that would possibly be useful?
I suspect the rate at which new users may try to create new accounts and type a wrong email address is too low to be noticed by reputation metrics.
My point was rather that if you are operating a service with human users, there is no need to deal with quoted local parts, mixed-case, non-ascii, etc. You will just run into bugs (oh, the user signed up on an iPhone and the email field was auto-capitalized and now they can't find their account?) for almost no marginal benefit.