I have notice at mail-err.log that sometimes i get this error for a windows 7 user (that IP belongs to the client, if add more accounts there i will receive more of this errors for each account user):
auth: Error: od(teste2,192.168.1.83,<WxTcCg9CJADAqAFT>): validate response: unable to lookup user record
My server is a MacosX with Server app3, and as a client i am using a windows 7 with outlook 2013.
All seems to be working fine.