After recently upgrading a client's exchange server from 2003 to 2010, I have run into an issue that I hope someone may have seen before.

The client runs a software package that is able to connect to a SMTP/POP server in order to send out emails to their users (within said software). On Exchange 2003, we simply setup a user and mailbox (in AD) and plugged the information into the software package.

After upgrading to Exchange 2010, that particular account is no longer able to send emails via the software package. The only account I am able to get to send an email (through said software) was if that particular account was part of the Domain Admin group.

Obviously, I don't want to leave a simple mailbox user as a DA.
My thought is that this is a security setting within the newer Exchange 2010.
I am curious to the particular setting that allows DA's to send emails this way, but no other user. And to find that setting and allow this particular user send emails (through said software).

Any thoughts and/or help would be appreciated.