I've not tried it with IMSMO yet but I have used AD to authenticate Traveler devices.

First, get DA configured to use AD (which you've done, this is for others) http://www-01.ibm.com/support/docview.wss?uid=swg21293255.  Choose an AD attribute to contain the Domino CN and populate.

Second, fill in the person document fields LTPA user name (this is the AD CN) and Active Directory (kerberos) logon name (this is LogonName@DOMAIN.NAME format).

Third, create Web SSO config doc and enable Windows single sign-on integration and enable Map names in LTPA tokens.

Forth, add the SSO config to your website doc and set the session authentication to Multiple Servers (SSO)

IMSMO uses the email address as the username which in our case is already in AD - its also the attribute used by SAML / ADFS.

I did a test by removing my person doc from the directory on the IMSMO server, thereby forcing it to look to DA for login. Login in Outlook failed.

IBM Mail Sync error dialogue box says "Configuration error. An unsupported authentication method was detected on your server". 

So I'd say it won't work. Anyone from IBM lurking? 

I should said I also tried blanking out the HTTP password at the same time as I tried removing my person doc as I'd read that document. Didn't work. 

So enabling SAML on all the mail servers has then meant that when a user clicks on the link to an archived email in Outlook it now opens a browser and displays the email along with normal operation buttons like reply, forward etc. Problem solved.