I am using Windows Live Mail in Windows 7.  When receiving any email with an attachment, I keep getting the message:

Your mailbox is over the high water mark.
Please delete some messages from your mailbox!

Some emails with attachments (even under 10 mb) get bounced back to the sender with a message that the In Box is full.

A message was sent to you that was returned to the sender(bounced)
because it would have caused your mailbox quota to be exceeded.

The following is the reason that the message was over quota:

       Quota Type: bytes in the mailbox
  Quota Available: 10175606
      Total Quota: 10240000

I currently have only 17 messages in the In-Box of this account, none heavy with attachments.  What is going on and how do I fix this?

thank you.