Creating & sending MIME file causing ATT00001.TXT attachment

We finally got around to replacing the awful SNDDST command
for sending emails.

We are now creating our own email messages (MIME files) with
as many attachments as we want.

Users love it.



Now the problem:

Using Exchange 2003 the emails are fine

With Exchange 2007 the user gets an extra attachment
ATT00001.TXT

This extra attachment contains the email message, if there
was no email message (subject only) then the extra
attachment is empty



The Google search I have done has pointed to charset issue
in Exchange 5.5, but we are specifying charset us-ascii when
the email message

Is text only (apparently we cannot use this when the email
message is html or mixed) but that's for another post.

Also, the issue is not specific to Exchange because it has
occurred also with GroupWise 7.0





Thanks

John