My mailbox is reporting as full.

If you receive a message saying that your mailbox is over its size limit, try the following steps:
 
The following steps will empty a mailbox:

• Delete all the items in the inbox that you don't want. Note any emails that are large in size.
• Empty the messages from other folders, especially Sent Items and Drafts.
• Empty the Deleted Items folder. Until you do this, all the items remain in the mailbox.

You will likely have to logout and login before these actions take effect.
 
(Optional): If in Outlook, you can turn on Auto Archive. Go to the Tools menu, then to Options, and click the Other tab. There you can select how often it emails are archived, and where the archives are saved.