Typically these .TMP files are incoming mail files in the process of being received over the net. Eventually they turn into .MAIL files or are deleted if the connection times out. If this does not happen, you can safely delete them after a reasonable amount of time (as an indication, the default timeout is 10 minutes so anything 11 minutes older or more can be safely deleted). You shouldn't have to do this manually though, not unless you had a crash or rebooted while a message was being received.

  Eric