I haven't seen a response to this posting yet (which could be at least
 partially due to the fact that the replies were directed back to the
 ACCESS-L list :)), so I thought I'd offer a few suggestions.
 
On Mon, 17 May 1993 15:44:14 EST Nathan Brindle said:
>Can anyone tell me why these things are going to the list?  We've had
>about 15 of them since Friday.  I deleted the user yesterday but apparently
>to no avail.  Thanks, Nathan  (BTW--they are going to the LIST, not to
>the account I use for errors.)
 
 I was going to trim this, but every line has something important in it.
 When some mail delivery errors start getting distributed to your list,
 it probably started innocently enough...  Some e-mail address on the
 list couldn't receive the mail sent out by the list, and the mail system
 on the receiving end (or on some local/regional gateway) bounced the
 mail back.  That's usually as far as it goes, since LISTSERV performs
 a variety of tests to determine if incoming mail is in fact a delivery
 notice.  However, if the form chosen by the system bouncing the mail is
 unusual enough, LISTSERV's checks may not flag the note as a mail
 delivery nastygram, and it's forwarded to the list.  Of course this is
 a very bad situation, since the address that couldn't receive mail in
 the first place gets sent a copy, which is returned as before, etc...
 creating a mailing loop.  And unfortunately, if the mail delivery
 problem involves a gateway that has queued mail for several days before
 returning it to the list, the delivery errors can continue to arrive for
 weeks after the subscriber has been removed from the list.  So, what can
 you do if/when you are unfortunate enough to find yourself in such a
 situation?  First and foremost, I would recommend HOLD'ing the list to
 prevent anymore mail from being sent out while you find/remove the bad
 e-mail address from the list.  Next, send mail to the postmaster at the
 site that is bouncing the mail.  You have to dredge through the mail
 headers of the recurring mail to figure out what system is generating
 the error notice.  Explain to the postmaster what is happening and they
 will probably be very willing to help fix the problem.  After all, the
 mail loop is causing their system to receive a lot of garbage too.  If
 there is mail queued for the problem address from the list, I'd try to
 get them to purge it.  I've had mixed success getting postmasters to
 muck with queued mail though, so hope for the best here. :)  Next, look
 at the headers of the mail that is being sent to your list.  If the
 "From:" line is consistent, or even if the addresses are similar each
 time, then you can configure your list to refuse any more mail rejection
 notices.  There's a list header keyword that was introduced with version
 1.7f of LISTSERV that can be used to block out addresses.  The FILTER
 keyword lets you add any number of addresses and/or partial addresses
 with wildcards to the list of refused sources.  So that if the mail
 delivery errors all contained the mail header line,
 
 From: [log in to unmask]
 
 in the headers, you could code,
 
       Filter=Also,zippo*@*.COM
 -or-  Filter=Also,[log in to unmask]
 
 and no more delivery errors from that address would be passed on to
 the list.  If you want a complete description of the FILTER header
 option, please check the LSTOWN-L archives.  Once you have added the
 appropriate address filter(s) to your list, you can safely FREE the
 list.  If the postmaster at the offending site couldn't be reached,
 your list should still be safe.  Even if there is already 3-7 days
 worth of mail queued at some gateway, it will be blocked whenever
 it's sent back to the list.  Just make sure to choose FILTER's that
 are sufficiently general to block the delivery errors.  And I'd keep
 an eye on the list at first too. :)  Any mail received that is
 refused by LISTSERV due to the FILTER keyword you've added will be
 forwarded to the address specified in the "Errors-To" keyword.
 
 -jj
 
 PS - Multiple addresses/patterns can be specified on the "Filter="
 keyword as follows,  Filter=Also,user*@node1,user@node2,user@*node3*
 where the addresses you want blocked are concatenated together after
 the "Also" parameter, separated by commas.  And unless you've read
 the complete description of how the "Filter" keyword works, I'd
 advise just coding "Also" as the first parameter.  If you want to
 read the full description, check the LSTOWN-L archives for Jan '93
 and search for the posting with the string,  Filter=  in the subject.
 And even after that, I'd recommend that you think carefully before
 using anything but "Also" as the first parameter. :)