We've got a couple of mailing lists at our site that are for announcements.
One has been around for a while and has been growing by leaps and bounds
until now it has about 15,000 members.  The other is about twice as large.

This past week, when they sent out mailings they got back some complaints
that the subscriber had received a message with no body.  Not everyone had
this problem (in fact these people seem to be a pretty small minority), but
this has never happened before.  In one case, one person was sent a full
copy of the message wheras another account at the same site was sent a
blank one (I take this information from bounce messages).

We're investigating this at our end, but has anyone here run into this
problem before, and if so what was the cause?

Thanks,
jwgh