would they not then block official port 587 as well as
That was the position I heard the 'customer service rep' take the last
time I tried to solve such a problem through appeal to bureaucratic sensibility.
There isn't really a (valid) reason to block port 587:
Blocking outgoing connections to port 25 may be done in order to block
some zombie-networks (but IMO this is just silly.. will they also block port 80
soon to stop this blog-spamming? .. anyway ..)
..but you cannot spam using port 587 (unless you've been hijacking a
An smtpd running on port 587 must not accept mails from unauthenticated
clients for any recipients:
Connected to smtpauth.bluewin.ch.
220 tr12.bluewin.ch ESMTP Service (Bluewin 7.3.121) ready
530 authentication required for mail submission
..only MUA/MSAs are supposed to use port 587.
(Did anyone ever see/know an ISP blocking 587 ?)