Hmm. For the filename I'm passing on to QtmmSendMail, I'm using a generated name based on the fully qualified jobname, and the time of day, only resolved down to seconds. Could it be that these messages are being queued up so fast that I need sub-second resolution when generating my temporary filenames?
Some of the messages I see in the QMSF joblog suggest that this may be it.
But if anybody has any other ideas, I'm open to them.