|        One of my lists (a private list at [log in to unmask])
|has *apparently* suffered this same problem. A member complained two
|messages didn't make it out; he received no errors; his address hasn't
|changed (I know because -->)
|
|        I asked him to send them again and cc me. He did. I received the cc
|(I checked the headers) but the list never generated the messages; again, he
|received no error and he did address them correctly. The administrator
|doesn't show them in their log. I tried a test message right after I
|received the cc's and it went okay.

LISTSERV(R) not receiving a message to distribute is entirely different
(well, maybe not entirely) than a list not distributing a message to a
subscriber.

Please remember that email is not 100% predictable.  Here at Penn State,
when a customer generates email, it is FIRST sent from their client SMTP
to an outbound "gateway" SMTP server (here at PSU).  That server (then
becomes a client and) is responsible for queuing and delivering the mail
to the TO:, CC: and BCC: Internet recipients' SMTP server.  It does NOT
do this with one big FIFO queue, but instead multiple queues running in
parallel.  It seldon but occassionally occurs that one of those queues
"hangs" and requires mail administrator intervention.

Furthermore, mail delivery is further mediated by the Domain Name System
(DNS) which most often uses multiple (and hierarchical) servers to
"resolve" the @node name to zero, one, or more Mail eXchangers (MX).  It
is not outside the realm of possibilities that the DNS structure was/is
out-of-sync, or the most preferred MX host was not available and a less
preferred MX host "handled" the mail (perhaps not as well as the preferred).

/Pete Weiss at Penn State