Thanks for your attempt to help me. Alas, so far unsuccesful (most likely my
shortcoming as you write books about this).

Re your solution (about Message formats), that is what MS Help keeps telling
me, but I can't make it work. Also, what I understand is that this is valid
for attached messages (not files). What I want is the same as for the BCC
field, selecting to show the field and when attaching a file (by dragging it
to the field), you see a small icon (DOC, PPT, PDF) and the name of the file
in that field.

The Help states that if format is HTML or Plain, the message will appear in
the Attach line. Basic problem is that I can't make this Attach line appear
in the Form.
I see TO, CC, BCC and Subject. Why not Attach??

Going to the Form designer and adding Attachment, all I get is attachment
with a small square, probably indicating Attachment Y/N.

Regards,
Michiel