[Slackbuilds-users] Bounce messages re mail loop

Rob McGee rob0 at slackbuilds.org
Tue May 19 05:16:52 UTC 2009

On Mon May 18 2009 22:29:56 Robby Workman wrote:
> It seems that a problem has come up within the last 24 hours or so in
> which valid mails are getting bounced, but not bounced.  In other
> words, the sender is being informed of a bounce due to a mail loop on
> the server, but the mail is going through anyway.
> We have no idea exactly what's going on, because none of us have made
> any changes to the mail configuration, and of course, the
> configuration looks correct :-)  rob0 is investigating and
> considering a call to Ghostbusters, so be patient.  In the meantime,
> ignore any bounced messages - status updates will be posted here as
> we get them.

Ghostbusters were not needed.

It was / is correct on our end. Every bounce came through one or more 
hosts at mo-p05-ob.rzone.de[] (x=0-2). I am still not 
entirely sure what they did, but my guess is that they have done a 
virtual alias or user .forward of slackbuilds-users at slackbuilds.org 
going *to* slackbuilds-users at slackbuilds.org. Obviously NOT a good 
idea. This is coming with the same envelope sender on each.

As of a few minutes ago, those hosts are blocked from sending mail to 
slackbuilds-users at slackbuilds.org. The rejection message will instruct 
the recipient to contact postmaster at slackbuilds.org to resolve the 

There were 15 total bounces sent today, beginning at May 18 14:36 and 
ending May 19 03:37 (times are UTC.) If you got one, sorry.

I think there's an exploitable issue here, so I will follow up to the 
postfix-users mailing list. It's not Mailman's fault, since the 
forwarding loop was detected and the bounces generated before the 
Mailman posting software was invoked.

Any problems, questions or concerns, please let me know, here or 

Rob - /dev/rob0

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