Outgoing Mail Control Question

[G J Piper]

In Plesk 12.5, if a mailbox exceeds it's limit for outgoing mail, and I go in and raise its limit, how can I reset the mailbox so it will now accept the new limit and resume sending? Currently the mailbox was set to 30, and I raised it to 99. But, even after a server restart it says the mail status for that mailbox is "Not Sending".