If you are getting the System Administrator message that your mailbox is too full, you can use the following tool to find out what messages or folders are causing this problem. After you narrow down where the problem is, you can delete, archive or move to a personal folder.

It is not the NUMBER of items that matter, but the total SIZE of all items.

Some people have been surprised to find that they were over the limit due to items in their calendar or tasks folder.

Reminder
Warning at 170000 KB
Prevent SEND at 180000 KB
Prevent SEND and RECEIVE at 200000 KB
(mailbox size increased from 140/150/170 on 5/25/2011).

To find out which items in your mailbox are causing you grief, do the following based on your version of Microsoft Office

office 2010
Click FILE,
Click CLEANUP TOOLS
Click Mailbox Cleanup
Click VEIW MAILBOX SIZE
At the top of the Folder size window, you should see "Total size (Including subfolders). This tells you the TOTAL amount of space you are currently using.

Scroll down through the list of folders using the SIZE column and see which folders are using the most space. Many times just knowing this, helps to figure out what needs to be deleted/archived. It might be your Sent items or Deleted items folder. The TOTAL SIZE column can be misleading - this figure will include the nested subfolders.

If this does not clear things up for you, click Close and then select the "Find items larger than" button and change the value to 1000 and click FIND. The results should show you all the items in your mailbox that are larger than 1MB. It will tell you what folder these items are in (not necessarily the Inbox).

From the mailbox cleanup window you can also force an archive, or empty your deleted items folder.

If you are still having problems with a full mailbox - call the Computer Center Help Desk at x1080.

Office 2007
Click Tools (at top)
click Mailbox Cleanup
Do any of the following:
   View the total size of your mailbox and of individual folders within it.
   Find items older than a certain date.
   Find items that are larger than a certain KB size.
   Archive items using AutoArchive.
   View the size of your Deleted Items folder.
   Empty your Deleted Items folder.

If you are still having problems with a full mailbox - call the Computer Center Help Desk at x1080.