On Sun, 13 Jun 1999 08:20:12 -0400, Pete Weiss <[log in to unmask]> wrote:

>Have said individual email the LISTSERV@listhost the command
>
>THANKS


I suggest slightly more:


THANKS
INFO listname


The answer to THANKS is returned (like many LISTSERV command responses) with a
RFC821 MAIL FROM:<>  (i.e. blank) which must be allowed (by RFC1123) but which
some mail systems incorrectly block.

The answer to INFO listname is returned with 
MAIL FROM:<owner-listname@host_name>  (i.e. non-blank) which is definitely
allowed.

So if they get 0 responses something very bad such as domain name or IP blocking
is going on.  If they get only 1 response to INFO listname, then the ISP is
blocking MAIL FROM:<>.  If they get both responses, then all is well (for direct
addressed mail) and the spam filter is perhaps blocking BSMTP mail.