Whenever I attempt to send an email with an attachment, I get the little yellow yield symbol with the exclamation point in it displayed in the lower right of the window.  This opens the error box which states " 5.2.3  Data Size Exceeds Maximun Permitted"

The attachments I send are often less than 1MB in size; it is a POP3 account; I have no access to the server.  Is there anything I can do, short of calling the ISP?