SASL Authentication Problem

[Dominik Göbl]

Hi everbody! 

I hope you can help me with this: 

I set up a test - mailserver with postfix, cyrus and cyrus-sasl. 
Anything works just fine. The only thing which drives me mad is the 
following: 

imapd.conf: 

configdirectory: /var/lib/imap 
partition-default: /var/spool/imap 
admins: cyrus 
sendmail: /usr/sbin/sendmail 
hashimapspool: true 
unixhierarchysep: 1 
virtdomains: userid 
defaultdomain: example.com 

Whenever I try to logon to cyrus and use a adress in the machine's 
realm/domain he automatically adds the hostname. For example I log on 
as: "foo AT example.com" sasl tries to lookup the user "foo" and the realm 
"mail.example.com". Not suprisingly I get a "Login failed". 
This does not happen if I log on as "Foo AT otherdomain.com"

I searched the documentation up and down and didn't find anything. 
Maybe I'm just ignoring some config-options. Anyway I would be glad if 
someone could help me 

best regards 
Dominik