[Kolab-devel] Read Receipt Error

Jeroen van Meeuwen (Kolab Systems) vanmeeuwen at kolabsys.com
Thu Feb 7 01:07:26 CET 2013

On 2013-02-06 19:22, Mat Cantin wrote:
> Greetings,

Hi Mat,

> My users on two different sites report not being able to send the 
> "Read
> Receipt" of a message. The dialogue box comes up asking if they wish 
> to
> send it, but when they hit ok they get this message: 451 4.3.5 Server
> configuration problem
> The servers are running CentOS 6.3 with the latest Kolab 3 stable
> release.

A fix was introduced in 

It should be included in the 0.9-beta for Roundcube we ship today, so 
setting that option to true might resolve the problem.

Please note that using the SMTP server that Roundcube is configured to 
use, a user is not allowed to send a message using an envelope sender 
that the user is not explicitly authorized to use - ergo, the envelope 
sender address must be a primary ('mail') or secondary mail ('alias') 
attribute value, or the user must have been explicitly delegated 
permission to send on behalf of another LDAP object (user, shared 
folder, etc.).

Roundcube was - rightfully so if the recommendations from the related 
RFCs are followed, to prevent unsolicited responses including NDRs from 
being returned, and MDN-loops - sending the MDN responses with an empty 
envelope sender address.

Kind regards,

Jeroen van Meeuwen

Systems Architect, Kolab Systems AG

e: vanmeeuwen at kolabsys.com
m: +44 74 2516 3817
w: http://www.kolabsys.com

pgp: 9342 BF08

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