Port 25 - Blacklash

[In the message entitled "Re: Port 25 - Blacklash" on Apr 26, 17:50, Daniel Golding writes:]

Do all of Comcast's markets block port 25? Is there a correlation between
spam volume and the ones that do (or don't)?

No. Yes. The ones that don't block port 25 emit more spam than the
ones that do.

In any event the malware is already ahead of port 25 blocking and is
leveraging ISP smarthosting. SMTP-Auth is the pill to ease this pain/

Correct. And/or rate limiting, by understanding which customers are using
which IP addresses (more or less tying the networking infrastructure to the
email infrastructure, which is something that many ISP are not yet doing).