Problem: A small group of external users were given AD accounts and domain user group membership, allowing them login access to the SharePoint intranet environment. These AD accounts were set up with the user’s email account from a different domain (in this case, a Gmail business account with an @contoso.com alias). These users were able to successfully set up a SharePoint alert on a document library without errors, but the users never received a confirmation email or any subsequent alert emails.
Cause: The Exchange server was preventing relay of the messages from SharePoint to the external domain.
Resolution: Within Exchange, the foreign domain was added to the list of Accepted Domains in the Hub Transport.
From within the Exchange Management Console:
Microsoft Exchange- Organization Configuration- Hub Transport – (tab) Accepted Domains – Add the needed External Relayed Domains
Caution: allowing mail relay to foreign domains, particularly common Internet domains such as gmail.com or yahoo.com, may present added security risks. See the Tech Net article referenced below for a discussion of techniques to mitigate these risks.
Many thanks are owed to System Administrator Dino Jaha and Exchange Administrator Jeff Noyes for researching this solution.
For more discussion of the hub transport role, email relaying, and screen shots of Exchange 2007, see Tech Net’s article: