Autodiscover for a primary domain is working perfectly.

However, when we add an alias domain to the account, along with setting up all the DNS records needed for autodiscover, it fails when a user tries to autodiscover on the domain alias.  For example:

BobSmith@domain.com   autodiscover works fine, but

BobSmith@aliased-domain.com  autodiscover fails.

When we run the Outlook connectivity test (CNTL-right-click Outlook tray icon and choose Test Email Autoconfiguration) it discovers the MAPI/Exchange services on the primary domain, but when we run it against the alias domain, it only discovers IMAP.  But it's the same account in SmarterMail.

What's the secret to getting Autodiscover to work with the alias domains?  And yes, having all users in the same account is a genuine need.  Company has 2 divisions, and each division uses their own domain name.  We put everyone into the same account because all users need access to the Global Address List and seamlessly share resources (using MAPI).