Hmmm... This isn't really a mail delivery problem, but an attachment problem, so relaying & DNS should therefore not be factors. We have no anti-spam e-mail product, and the A/V is the same on both of our MX servers (besides which, the messages are not being intercepted by AV, I would be able to see that). Tell me more about the peculiarities of the LISTSERV Distribute Backbone - that's one I haven't heard of. Thanks, Kerry -----Original Message----- From: Pete Weiss [mailto:[log in to unmask]] Sent: Saturday, May 03, 2003 7:33 AM To: [log in to unmask] Subject: Re: attachments are disappearing Some intermittant delivery (generic) problems are because some sites have multiple MX hosts which do not handle e-mail identically e.g. "we do not relay" or "userid not found" when the highest precedent MX host does just fine. Add to that list A/V and anti-spam protection of various servers. Then further add to that list the vagaries of DNS processing (out of synch among servers) and on top of that, the perculiarities of the LISTSERV Distribute Backbone. /Pete