I was asked by a client today to look into an issue with their resource mailboxes that stopped auto accepting calendar booking requests from users a month ago. After carefully reviewing the settings for the resource mailboxes, creating new ones to test and also moving arbitration mailboxes to other mailbox stores without any luck, I finally stopped and thought that maybe I should check the Microsoft Exchange Mailbox Assistants (MSExchangeMailboxAssistants.exe) service because the description clearly states the following: Performs background processing of mailboxes in the Exchange store.
To make a long story short, the service was indeed stopped:
Once the service was restarted, all of the queued up resource mailbox calendar bookings began to get processed. I’m writing this blog post because while performing searches on the internet, none of the first 5 results I searched for pointed towards checking the service.