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Comment by okasaki | Hacker News Reader

username+whatever@gmail.com is delivered to username@gmail.com, so if you add the service name when you sign up it's very easy to block unwanted traffic. It also tells you which service sold your email to spammers.

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Also, if you run your own sendmail you can just add the following completely readable snippet to your sendmail.mc:

  LOCAL_CONFIG
  Kplus regex -d+ -s1,2 ^([^._]+)[._](.+)$
  LOCAL_RULE_3
  R$* <@ $=w > $* $: $(plus $1 $) <@$2> $3

That allows you to use "username.whatever@example.com" or "username_whatever@example.com" as well as the "+".

A lot of web sites' idiot email validator regexes won't allow "+" in emails. But every single one allows "." and "_".

Unless the spammers simply run remove the extra part from the address. A better way is to get your own domain and use a different alias for each service.

I use a subdomain and forward *@subdomain.domain.com -- if you put a catchall on the root you will get spam.

I've been doing the + thing for more than 10 years now. My observation is that spammers simply don't remove it (it's just not worth their time).

More importantly, legit services that are on the spammy side (or have broken unsubscribe links) will absolutely never remove it.

Back a few years when Ameritrade had a bunch of its user's emails sold to spammers, I just changed my email on the ameritrade website and started blocking my +ameritrade address. It worked like a charm.

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