> There are a bezillion reasons why folks don't always get
> their email.  A
> comprehensive analysis would require knowing the userid@host
> in question,
> having them send some test messages to LISTSERV, having
> access to logs,
> using NSLOOKUP (perhaps recursively), sometimes contact with
> postmasters
> and ISPs (any blocking going on), etc.

The problem is, even LOCAL users have reported this problem. And
recently I have reproduced it with my own E-mail address which has never
experienced any problems.

When the LISTSERV log reads "Mail posted via SMTP to ..." and there is
no subsequent indication in of a delivery error to that address, it
indicates to me that the SMTP transaction was successful (i.e., no DNS
or transient errors).

This is a nearly impossible problem to solve because it is intermittent.
One reason we switched to LISTSERV for bulk mail was for more reliable
delivery, and now the client is questioning me on that...