Running Exchange 2013 with Outlook 2013 clients.
I have AD (2012 R2) users with mailboxes, that have also been granted SendAs and Full Access to various shared mailboxes.
These shared mailboxes automatically show up when the user logs into Windows and opens their Outlook 2013.
If they click on the People category in Outlook 2013, they can see Contacts, under My Contacts, from both their user mailbox (firstname.lastname@example.org) as well as from the shared mailbox. Therefore, I can confirm that they have access to contacts from both sources.
However, when they go to actually compose an email, and open the address book to search for contacts, none of the available options from the pull-down menu give them access to the contacts stored in the shared mailbox.
How can I fix this?