In Notes R5, mail.box is used for transmitting both native Notes and standard SMTP (Simple Mail Transfer Protocol) messages. In Notes 4.x, native Notes mail is routed through the mail.box database. Since Notes 4.x relies on the SMTP MTA (Mail Transfer Agent, or Internet email) for Internet mail delivery, SMTP-based temporary databases are involved.

We won't examine problems with the SMTP MTA here. For information on keeping your SMTP MTA running properly, check out the DominoPower article from February 1999 at http://www.dominopower.com/issues/issue199902/smtp001.html.

Periodically, the mail.box database can become corrupted. If it does, mail routing will stop. Any number of circumstances can cause corruption. There are literally millions of computers on the Internet, and millions of mail messages per day being transferred. Mail may become corrupted if one of those mail systems sends an ill-formed message to the Domino server and the server has problems interpreting or converting it.

Mail corruption may also happen because of network problems. During the transmittal of a mail message, network problems may cause corrupted packets of information, which in turn may corrupt the mail database. If you repeatedly have problems with corruption and are unable to find anything wrong with the Domino server environment, begin investigating potential network problems, such as malfunctioning network cards or buggy network drivers.

Server problems, such as low memory or the server running out of memory during mail transmittal, may also cause corruption. NT servers in particular have a higher tendency to leak memory. Over time this leak may cause the Domino server to run out of space, which it needs to perform message conversion and/or routing.

Getting the mail routing again
There are several other reasons as to why mail routing may have stopped. There's a high probability that if you haven't made changes to the Domino server environment, but mail routing has stopped anyway, that the cause is mail.box corruption.