[Kolab-devel] Mail Filter Settings, explain please.

[Christoph Wickert]

Am Donnerstag, 21. April 2011, 16:33:23 schrieb Robert Baldwin:
> Hello,  I need some assistance understanding the below features of the
> Kolab server.  I posted this question on the Kolab user's group and no one
> responded.  I hope that someone here has the expertise to answer my
> question.

Hi Robert,

sorry I didn't respond earlier. The problem with your particular question is 
that it is the settings are a) badly documented and b) don't actually do what 
the documentation says.

For a start I suggest you take a look at the German Handbook (sorry, no 
English translation available). On page there is a description of the settings 
and - even more important - on page 50 there is a diagram that describes the 
filter a little better - however it's not really 100% correct either.

For reference please have a look at https://issues.kolab.org/issue2449 and 
https://issues.kolab.org/issue2468. The complete story is outlined in  
https://issues.kolab.org/issue954 but be careful: it's long!

> What do these settings actually do? I am unable to determine this from
> the description.
> 
> Check messages for mismatching From header and envelope from:
> enabled: kolabfilter-verify-from-header: TRUE
> disabed: kolabfilter-verify-from-header: FALSE
> 
> Use the Sender header instead of From for the above checks if Sender is
> present :
> enabled: kolabfilter-allow-sender-header: TRUE
> disabled: kolabfilter-allow-sender-header: FALSE
> 
> Action to take for messages that fail the check: :
> Reject the message, except if it originates from the outside and the
>    From header matches one of Kolab server's domains. In that case rewrite
> the From header so the recipient can see the potential forgery.
> selected: kolabfilter-reject-forged-from-header: FALSE
> 
> Always reject the message. Note that enabling this setting will make the
> server reject any mail with non-matching sender and From header if the
> sender is an account on this server. This is known to cause trouble for
> example with mailinglists.
> selected: kolabfilter-reject-forged-from-header: TRUE

Note that the messages are not really rejected on a SMTP level because 
kolabfilter comes into action later. The mails are bounced instead as 
described in https://issues.kolab.org/issue2833

Regards,
Christoph

-- 
Christoph Wickert
Senior Engineer

Kolab Systems AG
Zürich, Switzerland

e: wickert at kolabsys.com
t: +49 251 871 369 77
w: http://kolabsys.com

pgp: 85DACC63 Christoph Wickert
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