Outlook Switching to Online Mode Even Though Cached Mode is Enabled

I have been dealing with an issue where a user's outlook would switch to online mode at random. The only way to resolve the issue was to log the user out of the computer and back in.

Re-creating the account resolved the issue, but it came back the next day. Procmon and ProcExp didn't point to any clear causes.

Eventually I was able to find the root cause by looking at the permissions of the mailboxes. The two mailboxes had Full Access to each other and auto mapping (never use auto mapping!) was enabled. This resulted in a situation where the mailboxes were fighting for who would be the primary mailbox, and who would be the secondary.

Removing the permissions resolved the issue and both mailboxes worked correctly inside of Outlook. 

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