Active Sync Cross-Site Redirection failure

Hi Team,

We have below Exchange Configuration

Sites - 2 sites (Active, Active)
DB copies - 2 copies in Site 1
                     1 copy in Site 2 (Remote passive)
2 sites have separate Internet facing with separate name spaces
a.mydomain.com
b.mydomain.com

Users mailboxes are distributed between 2 sites Exchange 2010 MBX servers.  

Due to capacity and performance issues, we are in position to move mailboxes and mount databases to the alternate sites.

When the mailboxes are activated in alternate site, OWA works fine by redirecting to home OWA URLs.  But mobile Activesync users having issues of not synchronizing the emails until they modify the OWA URL for the other site.

Why the mobile devices are not automatically configured when are moved/activated in the other site.  

Any suggestions for silent configuration for Active sync.

Thanks,
D