Outlook 2011 problem: identity synchronization with Exchange server

Outlook 2011 on Mac has stopped syncing properly with our Exchange server: folders stuck at old states, sync icons spinning forever and the error log filling with synchronization failures.

Webmail shows everything current so the server side is fine. Where does Outlook 2011 go wrong?

Outlook 2011 keeps everything, mail cache, sync state and settings, inside an identity, a database in your user Library. That database corrupting is the overwhelming cause of exactly these symptoms. The server being current in webmail confirms it: the identity's record of what has synced no longer matches reality and the client cannot reconcile.

1

Rebuild the identity with the bundled tool: quit Outlook, hold the Option key and launch Outlook again, which opens the Microsoft Database Utility instead.

2

Select your identity and click Rebuild. The utility copies the identity aside and reconstructs the database, taking a while proportional to mailbox size, leave it alone until done.

3

Launch Outlook normally afterwards. With Exchange the client now re-verifies folders against the server and the stuck states clear as the fresh database populates.

4

If rebuilding fails or the problems return within days, retire the identity instead: create a new one in the same utility, set it as default and add the Exchange account fresh. Since Exchange holds the mail server side, the new identity downloads a clean copy and nothing is lost.

Check the free space on the Mac before either step, identities double in size temporarily during a rebuild and a nearly full disk is itself a common trigger of the original corruption. And the era appropriate caveat applies here as elsewhere: 2011 is unsupported and its EWS dialect ages against modern Exchange, so recurring sync trouble on a healthy identity is often the server outgrowing the client rather than anything fixable locally.

Rebuild took about 40 minutes on my mailbox and every stuck folder cleared on the next sync pass. Disk was at 91% full which probably explains how it started.