How to Make Exchange's Autodiscover Work When Retain and Exchange Point to Different DNS

Customer's Exchange server and their Retain server are in different networks and do not point to the same DNS server as required by Exchange's autodiscover service; thus, autodiscover fails to resolve to a user's mailbox when setting up the Exchange module in Retain.

In this case, Retain is connecting to Exchange as a "client" in order to log into the users' mailboxes. 

The customer was able to make this work by creating a Conditional Forwarder in the DNS server to which his Retain server was pointing.  The Conditional Forwarder record pointed to the Exchange server's DNS server:

This article was originally published in the GWAVA knowledgebase as article ID 2233.