Rebuilding rarely fixes issues like this plus it can introduce problems to the Identity. Just think of it like having chemotherapy. While it might kill the cancer, it can also damage your body.
After you rebuild, you should always delete any IMAP and/or Exchange accounts and let them download from the server. Otherwise, the rebuild could have corrupted data in those account and it would sync back and overwrite the sever contents.
Your best option is to create a new Identity. If had never done a rebuild, then removing the account and adding it back would have been an acceptable option. If you choose this as the easy way out, don't be surprised when it all comes back to bite you in the future.
How to move your data to a new Identity
http://www.officeformachelp.com/2012/05/how-to-move-your-data-to-a-new-identity/
Connect Outlook for Mac 2011 to Gmail’s IMAP service
http://www.officeformachelp.com/2012/12/connect-outlook-for-mac-2011-to-gmails-i map-service/
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