Exchange 2007 Standard SP1. 100% Exchange 2007 orginization, 1 server. One of my users has a large mailbox which has gone over the default 2GB limit. I have cleared the checkboxes for the mail store limit options, and have also gone into the user's mailbox, unchecked the use default option, and left all the limit checkboxes cleared as well. I even tried setting the prohibit field to 0KB. When I log into his OWA, it still tells me the mailbox has exceeded the 2GB limit. At a loss, literally nothing online except for onethread on experts-exchange which had no solution.

An update. I tried to use the Set-MailboxDatabase cmdlet and set all three quota options to "unlimited". It completed with a message stating that the operation was succesful, but that no changes were made. This suggests to me that the syntax was correct but since the values were alreay unlimited that nothing would be changed.

I had this problem when I was trying to set the maxmessage size for outgoing mail. Try re-starting the Exchange services or re-boot the mail server. This worked for me.

That did the trick. Just restarted the Exchange mail store service and the size limit restrictions disapeared from the mailbox.

This article explained the reason. Mailbox Size Limits Are Not Enforced in a Reasonable Period of Time http://technet.microsoft.com/en-us/library/bb684892(EXCHG.80).aspx