Maximum number of outbound connections exceeded -- MMS 4.x.
This article was previously published as ID#26824

Summary:

The MMS SMTP Relay Properties allow the MMS administrator to specify the maximum number of simultaneous outbound SMTP connections that MMS can open. The default value is 10; the highest allowable setting is 99. This technote discusses the significance of this setting, and the ramifications of changing it from the default.

Symptom:

The MMS administrator may see events in the MMS log saying "Maximum number of outbound connections exceeded" (Event ID 108). This warning is not immediately critical, and may occur from time to time. But its frequent occurrence indicates that the MMS server is processing a lot of mail (or more than it used to).

Sometimes the frequency of this event increases when the MMS Relay Properties > Routing tab option is changed from Relay Server to DNS; DNS requires more outbound connections. The remainder of this technote discusses the scenario where the warning is caused by an increase in mail traffic, not just a change to DNS. You should continue reading, to see how to increase the connection limit.

Detailed Information:

If you do not increase the number of outbound connections, and the mail volume continues, mail will begin to backlog in the MMS Outbound queue, taking up more disk space. The queue will probably clear during off-peak hours, but will never clear if there is no let up in mail traffic.

The outbound connection limit can be changed on the MMS SMTP Relay Properties > Outbound tab.

If you do increase the outbound connection limit, you will increase the mail load downstream, out of MMS. Remember that "out of MMS" does not just mean out of your company to the Internet, it means "out of the MMS machine", which includes both out to the Internet and in to your internal mail server(s). So increasing the outbound connections will increase the load to all destinations, including your firewall, your ISP if you have an ISP, and internal mail servers.

Other considerations:

- If you raise your maximum outbound connections, you may need to
up the Maximum Domain Connections on the relay properties Limits
tab

- You could also try lowering the relay Connection Linger Timeout:

When a msg has been sent from MMS, MMS holds the
outbound SMTP connection open according to the number of seconds
in the registry key:

HKLM\Software\Worldtalk\WorldSecure Server\Pumps\SMTP Relay\
Connection Linger Timeout

The default value is 60 seconds. MMS does this as an
attempt to be efficient, so that subsequent mail msgs can also
be transferred over the same SMTP connection, and the SMTP
connection setup overhead is avoided. As an experiment, you can
try reducing this value to, say, 5 or 10 seconds, to see if that
makes a difference.

- Run netstat from a DOS prompt to ensure that connections are
closing down appropriately, i.e., that nothing is in the
LAST_ACK or FIN_SENT state, etc.

If connections are not closing down, consider Microsoft knowledge
base article Q254930:

Go to http://support.microsoft.com/, and search on Q254930.

Resolution:

We recommend increasing the outbound connections in increments of 5, until the frequency of the error message diminishes.

The whole problem is that your mail volume is increasing, either spiking several times during the day, or slowly increasing over time. In either case, you may need to scale your internal mail servers and your network hardware. If you have an ISP, your ISP's mail servers may even become involved at some point.

NOTE--

If you set outbound connections too high, it won't hurt MMS -- this value only protects the servers that MMS is delivering mail to. It can be lowered in case downstream servers can't handle the load.