[horde] Problem regarding Cyrus (?)

[Sebastian Lemke]

Hi @all,
 
i do not know, if I am at the right place for my question - I hope so.
I have setuped Cryus/Exim/IMP.
IMP is running; I can login and review my messages.
 
But when I would like to write a new email the following sender-email is
begin displayed:
s.lemke.infoworxx.de at infoworxx.de
 
But my email-address has to be:
s.lemke at infoworxx.de
 
I am using 
s.lemke.infoworxx.de
for my mailbox-name in cyrus.
 
Is it an IMP or Cyrus issue ? How can I fix it ? 
 
 
Regards,
Sebastian