Yep. A lot of big ISPs already block port 25 connections from residential lines.
That breaks a few things like the sendmail command on a default *Nix setup. But you can often set it up to relay mail to the ISP server instead.
It's a bit sad that you can't run a mail server at home. But very few people really need to do that. If you have a legitimate need to run your own mail server get a cheap cloud instance or use one of the bulk mail delivery services instead.
Blocking port 25 is a sane measure to protect Internet users from the spam and phishing mail propagated by botnets. Just like how some ISPs block the Windows networking ports to protect users with mis-configured home networks.
You usually can still run a mail server on your home connection. The port 25 block usually only blocks outgoing traffic. So you can still receive incoming email on port 25. You just need to make sure that you configure your mail server to smarthost all outgoing email via your ISPs MTA.
If you've got a dynamic IP, please don't even attempt this. If somebody else gets assigned your IP before you have a chance to update the DNS, they could potentially pick up your email.
Or use fetchmail to receive it and just use the smtp of whatever mail account provider you fetch from. Get your mail under Fourth Amendment protection and get around the port 25 blocking.
That breaks a few things like the sendmail command on a default *Nix setup. But you can often set it up to relay mail to the ISP server instead.
It's a bit sad that you can't run a mail server at home. But very few people really need to do that. If you have a legitimate need to run your own mail server get a cheap cloud instance or use one of the bulk mail delivery services instead.
Blocking port 25 is a sane measure to protect Internet users from the spam and phishing mail propagated by botnets. Just like how some ISPs block the Windows networking ports to protect users with mis-configured home networks.