At 9:12 PM -0400 6/12/02, dreambig.ap@pobox.com is rumored to have typed:
Text in the header.txt file is -not- included in an email if a file is attached to the email.
Yes it is. You simply cannot see it.
It's beyond the scope to explain what MIME is, define different MIME types, discuss how mail is displayed in MIME-aware email clients, etc. I will say that the header (or footer for that matter) _is_ prepended to the mail, but because it is outside any of the MIME sections it isn't _displayed._ The only way to _prove_ this is to telnet into the box and read your mail with a non-MIME-aware application like...well...mail. You'll see the header, then the first boundary section, the content type of the first section, then the second boundary, etc., etc.)
Short answer: The problem _isn't_ in the attachment, it's in the attachment changing the MIME type from text/plain to multipart/alternative and generating boundaried sections. Likely your header wouldn't display if someone sent a multipart/alternative with HTML in one section and text in the other, either.
Solution: prohibit non-text email. Harder solution: prepend a proper boundaried section of MIME type text/plain, using the _proper_ boundaries. Simplest solution: dump the header and add your info to the header fields (accepting that brain-dead applications like Outlook Express will hide them, anyway).
This _has_ been covered in the list before, since I remember typing this on more than one occasion (it may have even made it into the FAQ, I can't remember and am too lazy to look right now). But if my failing memory serves, it was almost always about appending footers, not prepending headers. (Same rules apply; outside the MIME boundaries, not displayed in MIME-aware email clients in multipart messages.)
Charlie