Answer: These users were remote users dialing into Mindspring and AT&T
Worldnet. Both of these ISP's have setup a per user block of port 25 to
prevent SPAM. I called AT&T and confirmed this and they removed the port
25 block. This is a new feature for them and was not affecting older
users of their Network, which accounted for why another AT&T dialup user
wasn't having the same problems.
Now I need to call Mindspring as well, I assume they will remove the block
without any problems.
All of the comments I got were very helpful, thanks to all!
=-=-=-=-=-=-=--==-
Question:
I've noticed a very strange problem with our mail server in the past few
weeks. At first, only one user had a problem, but now there are more
complaining of the identical problem.
Superficially, the problem is that they can receive mail, but cannot send.
Further investigation revealed that there were no entires in the mail.log
besides 'Connect from [IP]', and that was it. No error messages, or
connection refused messages etc. Furthermore, I've narrowed it down to
the port level. I was able to telnet to port 110 (or whatever the POP3
port is) just fine, but a telnet to port 25 just times out. This would
explain why people could receive but not send.
I thought the problem was indicitive of a TCP wrapper problem or
something, but I disabled wrappers and am still having the problem. Not
to mention, this has only happened with a few users dialing in to ISPs
such as mindspring and AT&T Worldnet.
I'm thinking it has something to do with the IP that is connecting because
other users on AT&T have been able to send just fine. And, of course, all
of our in-house people are working fine. I was completely stumped after
turning off TCP wrappers. What else could cause a refusal/timeout with a
certain port? Like I said, I can ping the machine and telnet to other
ports, just not 25.
Any ideas? We are running sendmail ver. 8.9.0 on an Alphaserver 1000 with
DU 4.0D.
-Ed Silver
Received on Fri Apr 28 2000 - 17:20:13 NZST