The message refers to the server that handles your mail, not
to your e-mail software. The server is operated by your Internet
service provider.
 
Your ISP allots a certain amount of space for your e-mail.
  If you don't get much mail, that means all of your old e-mail
has accumulated there over months or years. You've
finally filled your space.
There is a setting within your e-mail program that tells the server
to delete your e-mail after you've downloaded it. Otherwise, the
e-mail will simply be stored there.
   Call your ISP and ask that the e-mail be deleted from the server.
That will solve the immediate problem.
 
  Then fix your software so e-mail will be deleted from the
service automatically.
To do that:
In Outlook Express, click Tools>>Accounts. Click the Mail tab
and select the proper account. Click Properties>>Advanced. Clear
the box next to "Leave a copy of messages on server."
 
In Microsoft Outlook, click Tools>>E-mail Accounts. Select "View or
change existing e-mail accounts." Click Next. Select the proper
account
and click Change. Click Change and More Settings. Select the Advanced
tab. Clear the box next to "Leave a copy of messages on the server."
Click OK>>Next>>Finish.