SASL auth for selected users only

[Roel van Meer]

Hi,

is it possible *in Postfix* to configure the list of users for whom smtp  
auth is accepted?

I have smtp auth working, but I would like to exclude some accounts from  
using this functionality. I know it could be done in the sasl plugins (as  
documented in http://www.postfix.org/SASL_README.html#server_cyrus_comm) but  
I was wondering if this would be possible in Postfix itself.

Thanks!

Roel