On Thu, 27 Feb 2003, Theodore Ts'o wrote:
On Wed, Feb 26, 2003 at 07:49:15PM -0800, ietf1(_at_)ka9q(_dot_)net wrote:
Other widely deployed but similarly misguided anti-spam mechanisms
include blanket blocks on incoming or outgoing TCP connections to port
25. I've even encountered on ISP that transparently and silently
redirected my outbound SMTP connections to their own mail servers!
Yup, some 802.11 wireless "hotspot" networks block port 25 as well. Very
annoying. My personal workaround to this is to have a personal server
tucked away at a colo facility, which among other things, runs a SMTP
server listening on port 2025 (to get around the port 25 blocking
insanity). This SMTP server will relay e-mail on my behalf, no matter
when I am in the Internet, after my laptop uses STARTTLS and AUTH to
authenticate myself to my SMTP server.
Many sites, including my university, support STARTTLS+AUTH on the
Submission port (587, RFC 2476), which I believe is the recommended
service for clients to use to submit mail in any case (though not
well-supported among MUAs, to my knowledge), and also is effective at
getting around ISP blockage of port 25. Of course if it becomes very
popular the misguided ISPs will block it too.
- RL "Bob"