postfix client sends partial username/password to server

[Rob van Dam]

I use Postfix client on a Centos 5.5 Trixbox. Mail messages (voicemail 
notification) send to my password secured mailserver with Exim are 
refused. When I decode the used login credentials I see that only the 
first 14 characters of the username are used. My sasl_password looks 
like (yes i have changed the values):

mail.myserver.nl:25 log...@myserver.nl:n...@dlflewskr
The decode login string shows:
log...@myserve

....and the rest is cut off

Any idea how to solve this?

Regards,

Rob