Re-appearing Deleted Mail

[Mikel]

Has anyone had the problem of mail coming back. I delete mail from my inbox. 
Next I close Mozilla v0.9.1 on my NT 4 SP 6a workstation. I now open Mozilla 
again and log into my POP3 account. When I do this *some* email keeps coming 
back as if it is stored on the server. The 'Store on Server' Option for this 
account is not on. The mail that comes back doesn't even have a status of 'Read' 
either. Thanks in advance.