We have a user that gets the "mailbox full" warning every time he opens Outlook. Our company default is 2 GB, and his mailbox is at 2.14 GB. I set all Storage Quotas for his mailbox to unlimited (no boxes checked), but the error persists. 
Send and receive are not affected, nor are any other functions of Outlook (everything works fine). However, the user wants the "error" message to stop. How can I accomplish this? Thank you.
Mail client is Outlook 2013
Server is Exchange 2007 (on premise)
Best Answer
Option 1: By default it can take up to 2 hours for the change to be picked up by Exchange (as written in the official documentation here). The Microsoft Exchange Information Store service is responsible for enforcing mailbox size limits and uses a mailbox information cache to hold data on the mailbox including quota limits. So if you need to speed that up you might restart this service. But be warned, it will kick out all users who are currently connected with your Exchange server!
Option 2: You can assign Quotas per User Level and per DB level. Make sure that you adjusted the correct one.