You don’t mention what type of email here, but if your mailbox is full, the important part is to clear some size regardless of type. One of the best places to start (they are often forgotten) is to make sure that your Trash, or Deleted emails are emptied. Many people simply delete, but don’t ever empty, so the size never decreases. The next place to look is your sent mail – another area that rarely gets remembered when people clean up their email. Naturally your inbox – especially any back and forth email that contains attachments. Clean house, delete what you can and ask your IT Department about archiving – all of these steps will reduce the size of your mailbox.