They should also deal with the individual accounts etc, but thats the difficult problem.
You should self-host, so you can do the experiment for yourself. You might be surprised. You can always stop self-hosting if you don't like it.
For some time it was possible to just send a special request to the provider asking them to unblock the port, but this is becoming less common, for often they simply deny the request.
Users who have been hosting their own email for many years have often been grandfathered in so they might not even be aware of this.
I'm still refusing to give up the good fight.
Haven't had an issue since I moved to 365. Costs a little more but so much less hassle. I don't like it but I also need people to actually receive my emails.
Have yet to face deliverability issue with this setup (Gmail, outlook)
But I self-host email for ~20 years, and I have not managed to get rid of Spam without not also getting false positives.
I first used SpamAssistant, in later years Rspamd, but I feel like they are just not good enough. Also I find Rspamd config pretty incomprehensible.
Hosted email like also does not solve this, e.g. GMail filters way much (e.g. important company correspondence leading to orders almost being lost because they landed in our GMail spam, so I had to turn off the spam filter entirely).
I think techniques like HashCash by Adam Back should be revisited.
It would be better if we came up with new protocols that solve the email messaging problems and then gradually wean ourselves off email rather than trying to "fix" email.
In a sense this is already happening although instead of migrating to open protocols which solve the email problems we're migrating a lot of messaging to walled gardens which solve the problems (e.g. WhatsApp).
I had hoped that something useful would come out of blockchain technology that would allow for a better messaging protocol that was spam resistant, e2e encrypted and decentralized by design but I didnt see anything.
I completely agree with this.
Ironic given the amount of crypto spam that exists.
Of course this assumption is fully invalidated by open-access mail service providers: maintaining communication with xXx_kitty_slayer_xXx@tepidmail.com tells absolutely nothing about sincerity and authenticity of messages from DrJohnSmith@tepidmail.com. Not only there's roughly zero correlation, it could be argued that correlation is slightly negative if one does not expect out-of-the-blue contact attempts. Funnily enough, with the critical mass of non-spam migrating to providers, it becomes sort of positive signal, fueling feedback loop: even if the majority of spam came from gmail, messages from gmail would still be more likely to be non-spam than messages from rncrosoft.com, because most non-spam comes from there too.
On top of that, there's a lot of soft-spam. Companies will happily send out critical contract-related information and unwanted-unasked advertising from the very same domain and even the same address. The big providers are not shying away from selling shielding services to spam agencies.
That "someone" could - in theory - require pgpgpg signatures attached to messages and have origin-based filtering/ranking, but good luck convincing people to set up their gmail/outlook to even generate the signature, let alone publish it reliably/revocably. At the receiver end, your only reasonable bet is filtering/ranking the content. It's probably not a strictly uphill battle, but you definitely need significant amount of volume and tagging before your models become good enough and it stops to the case.
In reality, even if it sounds a bit ironic given above, the best route to fixing this is self hosting, especially in the cases where your messages are needed. The more people try to send mail from their self-hosted instances and insisted that it was the problem of the other end to complain to their service providers if they do not receive the messages, the less hegemony the cartel providers would have. And maybe we could have some sort of client auth for email.