I'm running an XP Pro (SP1
+ hotfixes) box on a domain-network consisting primarily of 2K boxes and I have a mysterious problem with my machine.
Immediately after I've restarted the machine I can use Outlook to send mail (SMTP
on port 25) and I can telnet to our mail server via port 25, but after a short while it seems as if port 25 is being blocked somehow, Outlook claims that it cannot connect to the server and a telnet attempt via port 25 gives this result "Connecting To [mail server]...Could not open connection to the host, on port 25: Connect failed."
The IMAP service on the mail server works flawlessly all the time and I can send mail via the web mail interface on the server (port 80).
If I go to a 2K box on the network, I have no problem telnetting to port 25 and I get the 220 ESMTP prompt just fine. So the SMTP
service is running just fine on the mail server.
I've been using my machine as a local webserver for a few sites I've been working on and IIS had started the local SMTP
service on the machine as well, so I stopped that service thinking that might block the port somehow, but that's not changed anything. I still cannot connect to/from port 25.
Our network is firewalled by a hardware firewall, so I'm not running any third party software firewall, and I've checked that I'd not inadvertently activated XP's own ICF.
I've tried connecting to the server using it's IP
, Short network name and it's fully qualified domain name, and all of these work fine with Ping and HTTP
access it's just SMTP
that doesn't work.
My machine is on the same subnet as the mail server, and some of the 2K boxes I've tested with are on different subnets, and they still connect just fine.
The mail server is a Windows Server 2003 (continually updated with hotfixes) box running MDaemon (latest version), but there is no real problem there as everyone else connects just fine.
I've chosen to place this in the Win XP section rather than in the "Network" or "Other programs" section because this only seems to affect the XP machine I'm using and not any of the 2K boxes on the network, and since I can't even telnet via the port in question it doesn't seem like a specific Outlook problem either.
Any suggestions are welcomed...