Global Sync User Question

We have been using ADI for connecting our employee intranet to Active Directory for several years. We’re in the process of building out a new intranet using WordPress on a different server and have decided to change to ADI NX due to development ceasing on the old plug-in.

My question is this:

I think we’ve set everything up using the ADI NX preferences but when we test the connection to our Active Directory, we’re getting the following warning:

Username for the sync user does not contain a correct suffix. If the connection to the ad fails, this could be the cause. Please make sure you added the right suffix to your global sync user at BlogOptions->Syncronizer.

I have not been able to figure out where this setting is located? Can someone point me in the right direction?

Thanks for any help you can give.