I work on a company that has two BE servers and one FE, lately in one of the servers, the Mailbox Store has got dismounted unexpectedly by looking to the Event Viewer I found this error message "The MAPI call 'OpenMsgStore' failed with the following error:
The attempt to log on to the Microsoft Exchange Server computer has failed.
The MAPI provider failed.
Microsoft Exchange Server Information Store
ID no: 8004011d-0512-00000000"
And also this error message "Exchange store 'First Storage Group\Mailbox Store (TTI-XCH-01)': The logical size of this database (the logical size equals the physical size of the .edb file and the .stm file minus the logical free space in each) is 18 GB. This database size has exceeded the size limit of 18 GB.
This database will be dismounted immediately."
What are my options to resolve this issue besides decreasing users mailboxes sizes?