Outgoing Status: Failure - An error occured while checking the connection to the Microsoft Dynamics server MS CRM 2011 Email Router configuration

while i was configuring Email Router for MS CRM 2011, i got the below error.
the profile and load users and queue is perfect, but when i click test access i got the below error.

no error logs also i found.
then i just changed the MS CRM 2011 Email Router service account from network to a domain account and then it started working and perfect...

regards,
yes.sudhanshu