Unsollicited Bulk Email

[Brian Shaw]

Erik,
  I would start with determining if it is just one destination that is blocking your users or many.  If it is one you should be able to contact them and find out why they are blocking you and how fix it.  Or, if it is many, contact the RBL sites to see which one has black listed your domain.
  In the past when I have had this issue the RBL maintainers have been pretty easy to work with.
  Good luck.

Brian
________________________________
From: Erik Kramer <erikkramer at gmail.com>
Sent: Aug 19, 2017 11:04 AM
To: users at lists.kolab.org
Subject: Unsollicited Bulk Email

Hi,

I run a multi domain mail server (Kolab 3.4).

And since yesterday my users receive a message like below, when sending a message.

Any ideas on how to fix it?

Thanks for your help,


Erik


A message from <XXXX>
to: XXXX

was considered unsolicited bulk e-mail (UBE).

Our internal reference code for your message is 02611-06/Wb81Bb8nbs25

The message carried your return address, so it was either a genuine mail
from you, or a sender address was faked and your e-mail address abused
by third party, in which case we apologize for undesired notification.

We do try to minimize backscatter for more prominent cases of UBE and
for infected mail, but for less obvious cases some balance between
losing genuine mail and sending undesired backscatter is sought,
and there can be some collateral damage on either side.

First upstream SMTP client IP address: [XXX.XXX.XXX] 

Return-Path: XXXX
From: XXXX
Sender: XXXXX
Message-ID: XXXXXX

Delivery of the email was stopped!
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