SMTP: Loss of Available Free Memory During Operation

The information in this article applies to:

• Microsoft Mail Gateway to SMTP, version 3.0

SYMPTOMS

During operation of the SMTP gateway, the available memory can unexpectedly decrease, and eventually it will interfere with the ability of the gateway to process mail.

CAUSE

Memory loss can occur if an incoming message contains two subject lines. Memory allocated for the first subject is not released after processing the message.

If you stop and restart the gateway, it will restore the free memory pool. The -BR option can be used to stop the gateway after a designated period of time.

For additional information, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q96126
   TITLE     : SMTP: Error in Documentation for -BR Parameter

STATUS

Microsoft has confirmed this to be a problem in version 3.0.9 of the Microsoft Mail Gateway to SMTP. A fix for this problem is in development, but has not been regression-tested and may be destabilizing in production environments. Contact Microsoft Product Support Services for more information on the availability of this fix.

MORE INFORMATION

Ordinarily a message will have only one subject, and when the second subject occurs, the memory allocated for the first subject is not released. The memory allocated for the subject is generally less than 40 bytes, but the position of the memory can fragment the free memory pool and result in failures when it attempts to allocate additional memory.

For additional information on how to observe the free memory during the gateway operation, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q108374
   TITLE     : SMTP: How to Find Available Memory