If you've received the error... "The size limit of X MB for mailbox 'your e-mail address' has been exceeded. Incoming mail to that mailbox is currently being rejected."
It means your email on the SERVER is full. It has nothing to do with your mail program (Outlook, etc.).
To fix the problem, log on using the Webmail system at mail.yourdomainname.ext. Click on the Reports icon to view a detailed report of your disk usage and remove some messages.
Note: All messages, Sent, Junk E-Mail, and your Inbox all count towards your limit.
First open your browser (Internet Explorer, Firefox etc.) and type in http://mail.domainname.ext
Note: Do not type in the www
The SmarterMail login screen will appear
Click on the Reports
icon in the left tree view to view Disk Usage Summary. This report will tell you the amount of disk space currently being used as well as the usage for each folder.
Using this as a guide, review and then delete messages until the error message subsides or in most cases the Max disk space is less than 100 mb. To find out your max disk space view Disk Usage Summary.
The most frequent cause of this error is leaving messages on the server rather than removing them from the server when you retrieve them. These settings are available on the Advanced tab within the account properties of Outlook and Outlook Express. See Below to change settings in Outlook 2007.
Remove from Server - Outlook 2007
||Click to Leave a copy of messages on the server. Next choose the number of days to Remove from the server.
Checking this will automatically delete the email from the server (SmarterMail) after the specified number of days.
Note: If left unchecked the email will stay on the server (SmarterMail) indefinitely. This will continue to take up space in your mailbox.
Eventually you will receive the message that your mailbox is full. (“The size limit of X MB for mailbox 'your e-mail address' has been exceeded. Incoming mail to that mailbox is currently being rejected.”)