While this list is not exhaustive, it should be helpful to those of
 you who would like a better understanding of how Listserv determines
 when to reject a mail file.  But do keep the following in mind.  If
 a Listserv site does not have LOOPCHK set to FULL, then some of these
 tests will not be done.  Also, JHUVM's Listserv code is version 1.6e
 and the EXEC that performs all these checks, LSVXMAIL, was last changed
 on September 17, 1990.  I cannot speak to what other Listserv versions
 or other LSVXMAIL's will do.  And ListEarn could be completely different
 for all I know.  The rejection scenarios I have not described relate to
 unexpected return codes from service routines, checks specifically for
 IBM NOTE files, etc...  Since the intent of this message is to provide
 information for people who run mail delivery systems, and mail gateways
 I've only included the test that are related to RFC822 header values.
 All test are done after collapsing the text to upper case.  And finally,
 thanks to Eric for fine tuning this list and pointing out a few checks
 I hadn't included.
 
 Having said that, Listserv will refuse to post a mail message to a
 mailing list, if any of the following conditions are found to be true.
 
 - The user portion of the Sender: tag is the userid associated with the
   mailing list to which the mail was to be distributed and the node
   portion of the Sender: tag is the name (or domain style name) of the
   local machine.
   (Ex:  Mail sent to VFORT-L@JHUVM with "Sender: VFORT-L@JHUVM")
 
 - The From: field indicates that the mail is from the local MAILER
   account.
 
 - The userid portion of the From: field contains the word "MAILER"
   after the characters '%', '!', and '.' are translated to blanks.
   (By "userid portion" I mean everything to the left of the '@' sign.)
 
 - The userid portion of the From: field contains the string "DAEMON"
 
 - The userid portsion of the From: field contains the word "LISTSERV"
   after the characters '%', '!', and '.' are translated to blanks.
 
 - Starting with Listserv version 1.7, if the word "POSTMASTER" or
   "UUCP" appaear in the userid portion of the From: line, the mail
   will be rejected.
 
 - If the address listed in the From: field is registered as a
   MAILER address in XMAILER NAMES.  That is, the userid portion of
   the From: field matches the :MAILER tag in XMAILER NAMES for
   the origin node.
 
 - If the node portion of the From: field maps to a registered gateway
   in DOMAIN NAMES and the userid portion of the From: field matches
   the :MAILER tag for that entry.
 
 - The value of the Subject: field starts with the string "UNDELIVER"
   or "UNABLE TO DELIVER MAIL".
 
 - The whole value of the Subject: field is "RETURNED NETWORK MAIL".
 
 - If the body of the mail message contains lines starting with any
   of the following strings: "Sender:", "From:", or "Reply-to:", then
   further comparisons are made.  If text to the right of the imbedded
   header (concatenated with the subsequent line from the mail body if
   it starts with a blank or a tab), contains the list name followed
   by the local node name (or register domain style name for the local
   node), then the file is rejected.  The file is also rejected if the
   text contains the local node (or alias) followed by the list name.
   In either case, the words must appear in the text seperated by one
   or more blanks after the characters '<>()@%!":' are translated to
   blanks.  Please note, that the imbedded headers must start in column
   one of the message text (or be preceeded only by blanks) for these
   tests to be performed.
 
   Note: This is a very intuitive test, it's just hard to explain in
   exact detail.  It detects messages containing mail headers that
   refer to back to the same mailing list.
 
 - If some maximum number of "To:" headers are found in the body of the
   mail message.  This number is configurable and defaults to 10.
 
 - If the file contains invalid RFC822 headers.
 
 - If LISTSERV  determines that  the message  is likely  to be  a LISTSERV
   command, erroneously sent to the list rather than the LISTSERV address.
 
 - If LISTSERV determines that a message with identical body (but possibly
   different headers - in particular,  "Received:" tags would be likely to
   be different) has been "recently" distributed to the list.
 
 ----------
 -jj