An Outlook 2003 user received the message below:
You have exceeded the size limit on your mailbox. You can find types of items to delete or move, empty the deleted items folder, or you can have Outlook transfer items to an archive file.
I had to delete copies of messages he forwarded multiple times and archive some messages to bring the mailbox size below 2 GigaBytes (GB) [See Outlook 2003 Mailbox Size Exceeded].
I also checked the size of all other users' mailboxes on the Microsoft Exchange 6.5 server that processes his email. [See Determining Mailbox Size for All Exchange Users]