I have a user that is receiving the following message when trying to send email to recipients within our Exchange 2003 organization. Her mailbox is well beneath the 100mb limit and there are no mailbox limits set specifically for her. "The message failed to be submitted because the storage limit for the mailbox that is submitting the message has been exceeded."
I cannot find a valid reason that she would be receiving this message. It does not happen all of the time, in fact she can send another message to the same user and not receive the error.