Opening and examining the dead messages will give an explanation as to the problem. In the example message shown in Figure B, the message attempted delivery to an invalid email address.

FIGURE B


You can look inside a dead message (kind of like performing an autopsy) to look for clues of what went wrong. Roll over picture for a larger image.

Your users use email to communicate with (potentially) thousands of other systems via SMTP. This means that your server will attempt SMTP communications with the myriad of SMTP servers on the Internet. While SMTP is a defined standard, vendors may interpret the standard differently -- which often results in slight differences in how SMTP conversions are done and how dissimilar SMTP servers communicate. These slight differences may be enough to cause problems of email communications between one system and another.

The bottom line is that it is not uncommon to find dead mail messages in the work queue databases.

Routine maintenance and housekeeping
Mail routing databases are somewhat unique within the Domino environment. Their existence requires that documents are continually being created and then deleted, sometimes at a very high rate.

By default, the SMTP MTA performs a "housekeeping" task every night at 1:00 am. During housekeeping, the MTA tasks are temporarily shut down. The work queue databases and the smtp.box database are compacted during this time. After housekeeping is complete, the SMTP MTA tasks are restarted.

It is important to know that the housekeeping process does not remove dead messages from the work queues. These messages should be periodically reviewed (as discussed above) and then manually deleted from the queue databases. Once the dead messages are deleted, the queue databases should be compacted.

During normal operation, deleted documents leave empty gaps within the databases. These gaps of void former document space are typically filled in during the creation of additional messages. Some free space will remain (since not all of the messages are of equal length and cannot fully fill existing free "slots), and the databases will grow over time.

Mail routing performs best when the mail routing databases are compacted regularly. Therefore you should perform manual maintenance of these databases on a periodic basis.

Database corruption
Queue databases are Notes databases and are therefore susceptible to the same problems as any other Notes database. Like other Notes databases, SMTP MTA queue file databases can become corrupt. Database corruption is more common in systems where the users are sending large attachments on a regular basis, and the SMTP MTA has been implemented upon a system that has questionable resources -- such as insufficient memory or drive space.

The SMTP MTA is like any other server-based process -- it performs much better when there is ample memory and disk space available. If large attachments are being transferred, the SMTP MTA server must (obviously) have ample disk space available as well.