Comment 4 for bug 266360

If filter_content is set to 'no', Mailman does no content
filtering.

Other things which Mailman does that may affect the MIME
structure of the message are adding msg_header and/or
msg_footer and scrubbing messages as controlled by
scrub_nondigest.

If the .vcf attachment is being removed and filter_content
and scrub_nondigest are both 'no', I think it is not Mailman
that's removing it.