Aha! You've ran into a common problem with /tmp.
Do the following
Page down twice
Restricted rename and unlink . . . . . : Yes
If you see this then
CHGATR OBJ('/tmp') ATR(*RSTDRNMUNL) VALUE(*NO) SUBTREE(*ALL)
This causes all sorts of issues. Apparently this is a common behavior
with /tmp directories in linux or Aix and IBM added this property some
releases ago. You should quickly change it. What happens is
ROB creates a file (ie MYATTACHMENT) in some subdirectory off of /tmp. Now
IBM's smtp client takes that attachment and tries to send it off in an
email. This runs as some other user, like QTCP. Even if you give QTCP
*allobj and everything else it cannot delete MYATTACHMENT when done
because of this *RSTDRNMUNL property.
See if this fixes it.
Read the help on CHGATR for more information.
Think of it as the world's crappiest attempt to emulate QTEMP in the IFS.