Exchange 2013, CU6, Outlook2013

User can't register calender items on outlook due to below error.

Error: The message store has reached its maximum size. To reduce the amount of data in this message store, select some items that you no longer need, permanently (Shift + Del) delete them

User's Mailbox size is not reached to full size at all.

Any solution?

Hello

check deleted item size  with: Get-MailboxStatistics a |fl if near 30 GB need delete from recovery deleted item.

thanks, I changed the size quota, it was solved.