We have an exchange 2010 multi tenant server up and running for quite some time. Everything is working well with one exception. We have several hosted domains where users have more than 1 email address. We can add additional accepted domains and associated email addresses to each user account without issue. The user receives emails from all addresses with no problems as well. However in outlook, after adding both addresses as accounts, we will have an option to change the "from" address to one of the additional email addresses when sending mail. The email is sent and received at the destination, but still with the default "from" address. Changing the from address to any other address listed has no effect. I am at a loss as everything else seems to work perfectly. Any suggestions?