​got me there, I don't do too much with images.  However, how are you testing this?  I'm reading mail with MS Outlook Web App (OWA) and in usual email, often have problems with a friend's pics ... he is using a Mac.  Have never had the time to track down the cause.

 Lsoft has this cautionary note in its docs:

The ability of LISTSERV to filter or reject messages that contain MIME attachments is completely dependent on the ability of the poster's mail client to properly identify the MIME attachment when the mail is originally sent.  

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