Many times people send extremely large emails; there may be several large digital pictures or other large attachments. If you are on dial up or a slower ISDN connection the large emails can take a long time to download.
Ways to fix the problem
Access your webmail to remove the large email. When you delete the file on the server (webmail) be sure to delete it from your trash so it doesn't fill up your email box. Click here for instructions on webmail
You may want to contact the individual who is sending the large emails and explain that it is causing problems with your email downloads and to not send such large files.