[Mailman-Users] Bounce processing questions (feature, or bug?)

[Hank van Cleef]

The esteemed Barry Finkel has said:
> 
> Hank van Cleef <vancleef at lostwells.net> wrote, in part,
> 
> >Basically, mail to verizon.net addresses failed and bounced for a 24
> >hour period on the 12th.  Service appeared to have been restored on
> >the 13th.  Again, yesterday (the 18th), Verizon quit receiving mail
> >again.  The log message being shown by sendmail is of the the form:
> >
> >Jun 19 10:49:00 julie sendmail[16973]: [ID 801593 mail.info]
> >m5JGmxNk016971: to=<customer at verizon.net>,
> >ctladdr=<vancleef at julie.lostwells.net> (101/10), delay=00:00:00,
> >xdelay=00:00:00, mailer=esmtp, pri=121428, relay=relay.verizon.net.
> >[206.46.232.11], dsn=5.0.0, stat=Service unavailable
> >
> >For the four days June 13-17, mail went verizon.net normally,
> >dsn-2.0.0, stat=Sent 
> >
> >Two Verizon users have contacted me and told me that they had received
> >no mail from our list since the 11th; that they had contacted Verizon
> >support, and had been told that Verizon was not blocking or dumping
> >our list mails.  
> 
> It seems to me that 
> 
>      stat=Service unavailable
> 
> means that the inbound mailer is not available at the moment.
> This should result in a 400-level SMTP retryable reject, not a
> 500-level hard reject.  The statement
> 
>      "Verizon was not blocking or dumping our list mails"
> 
> is technically a correct statement; Verizon is not accepting mail.
> 
> Another thought comes to mind - when this happens, is Verizon rejecting
> all mail, or is that mailer selectively not accepting mail?  If
> Verizon is selectively rejecting mail, then I would expect a different
> message than
> 
>      dsn=5.0.0 stat=Service unavailable.
> 
Since I'm the original poster, I should perhaps clarify a few things.
My real question, which Mark answered (thank you Mark) was about an
unwanted side effect from the Mailman bounce processor.  

When I made my original post, I decided to summarize my problems with
verizon.net, and develop my rationale for resetting the bounce
processing parameters as a diagnostic tool.  Given the recent thread
on problems with Hotmail, and other discussions about ISP's
spam-blocking Mailman mail list mails over time, I felt that including
some of the details could be informative to the larger audience of
Mailman-users readers.

First off, list mail deliveries to verizon.net (and yahoo.com) addresses
have always been slow.  My daily log-reading has led me to expect a
great deal of mail requeuing from those two sites on a daily basis,
and sporadic random bounces.  So I'm not "psyched up" to pay a lot of
attention to increases in "problem" activity from those two sites.

Bounces with dsn=5.0.0 from verizon aren't news to me. I felt that the
complete blackout on the 12th was very suspicious, but when service
resumed on the 13th, none of the affected verizon.net list members had
hit the bounce trap, so I did not have any of the bounce messages
being sent back to my site.

I had several offlist communications with one verizon.net subscriber
who did not receive mail after June 11.  I sent him the log messages I
had from the 12th (bounces) and the 13th (normal delivery) and told
him to work the problem with Verizon from his end.  His report back to
me was that Verizon had told him they were not purposely blocking our
list mail nor dumping it after receiving it.  

When Verizon reinstated the block on the 18th, an offlist mail to this
user bounced, which was the first hard evidence I had that we were
dealing with a purposeful and specific blacklist action by Verizon.  I
forwarded the bounce message to this user through another (unblocked)
IP to the user and told him to work the problem from his end with the
hard evidence I'd furnished.  

I reset the bounce score so that all of the active verizon.net would
bounce-disable almost immediately, which they did.  I forwarded
several of the bounce messages to other verizon.net users, and am
aware that several of them used them in dealing with the Verizon
administrators.  

I did go to the web site listed in the bounce messages and fill out
the form with my site information.  And I did get a response from
Verizon that they would remove the block.  The block was removed
around noon on the 20th, and for the moment, mail is now going to the
verizon.net listers and being delivered.  

I'm documenting this to the Mailman-users list in hopes that it is
useful and informative information for other administrators
encountering similar problems with user ISP's.  I've been through this
drill before with other ISP's.  Misinformation seems to be a standard
problem in communications between ISP's and their users, and giving
the users the log information from the sending site clears the air in
a hurry.  I make it clear to the affected users that if reliable mail
service cannot be restored, they will have to move to a site that will
accept list e-mail, but go no further than that.  

As Mark has mentioned, the dsn=5.0.0 is legitimate, but it certainly
is not very informative in a case like this.  

Hank