XFOR: Should Have Exclusive Access to Port 25 (146157)
The information in this article applies to:
- Microsoft Exchange Server 4.0
This article was previously published under Q146157 SYMPTOMS
The Microsoft Exchange Internet Mail Connector (IMC) requires exclusive use
of TCP port 25 to successfully transport SMTP mail. If another program
reserves port 25, the IMC may start without error, but no incoming
mail will be accepted.
CAUSE
The Internet Mail Connector uses TCP port 25 for inbound SMTP mail as
defined by RFC-821. For inbound SMTP mail, the IMC monitors port 25 for
incoming connections from other SMTP hosts. The IMC will answer all
incoming SMTP calls if it is the first or only SMTP service running.
If another SMTP service is running and set to receive mail, the Internet
Mail Connector will start without error, but incoming mail will not be
delivered to the Information Store. Incoming SMTP mail may be delivered to
the third party program's delivery queue, or it may be rejected and
returnedto the originating host.
The IMC may be able to deliver outbound mail even if another SMTP host is
monitoring port 25 for incoming mail. Multiple outbound connections are
possible, and when outbound mail is to be delivered, the IMC opens one or
more connections to port 25 to connect to other SMTP hosts.
RESOLUTION
Do not run third party SMTP applications on any Microsoft Exchange server
that is running the Internet Mail Connector service. You can verify if you
have another SMTP service running by using the Windows NT telnet program.
To test the connection, run telnet from the Windows NT command prompt
specifying the IP address of the server running the Internet Mail
Connector, for example:
By default, the IMC will respond with a greeting similar to:
220 imc.company.com service ready
If the response is worded differenty, you may have a third party SMTP
service that is running that you should disable to allow the Internet Mail
Connector to transfer SMTP mail.
Modification Type: | Minor | Last Reviewed: | 4/28/2005 |
---|
Keywords: | kbprb kbusage KB146157 |
---|
|