Port 25 closing?

[Ashley M. Kirchner]

    This is slightly OT, but ti's been driving me nuts, so I'm hoping
someone here might have some suggestions as to what to look for here.  I
have one Windows XP (SP2) machine that seems to randomly prevent
connections to our mail server via port 25.  Our internal network
connects to our mail server, which is outside of our firewall and only
this one machine is having this problem.  For no apparent reason at all
it will suddenly deny all connections made to the mail server through
port 25 (it can still RECEIVE e-mail since that goes over secure IMAP
port, but it can't send.)  I can log onto the firewall, and everything
works as far as opening a connection to the mail server.  I can get onto
a different machine on the network, and connect to the mail server just
fine, so I know it's not a firewall issue.  It's just this ONE XP
machine that's experiencing this problem.  And it only started happening
after installing SP2.  Looking in Windows' firewall log, there's nothing
that points to port 25 being blocked.  I can't telnet (to anything on
port 25, anywhere) from that machine, can't send e-mail, nothing.  The
solution?  Reboot the machine, and suddenly everything works again.  So,
what gives?

-- 
W | I haven't lost my mind; it's backed up on tape somewhere.
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  Ashley M. Kirchner <mailto:ashley at pcraft.com>   .   303.442.6410 x130
  IT Director / SysAdmin / Websmith             .     800.441.3873 x130
  Photo Craft Laboratories, Inc.            .     3550 Arapahoe Ave. #6
  http://www.pcraft.com ..... .  .    .       Boulder, CO 80303, U.S.A.