Agree with dannyb, Mailwasher click here is brilliant. You can view your email with no danger as it is in fact still on the mail server. Used it all the time til I went on broadband, used to get shed loads of SPAM and it was a real godsend (mailwasher that is).
So easy to use.You can select you Address Book as Friends, and it will let all of them through, but others will automatically have a delete tick against them. Process your mail and the deleted items will not be downloaded to you computer. It's Great. You can tick the mail as Friend,delete, bounce, etc.
However, if a new contact is not yet listed in your Address Book and you hastily click Process Mail to your Default In Box, the mail is deleted. But in MailwasherPro, you can easily restore accidentally deleted emails with just a few clicks. For more details either ask Mailwasher Help or ask here.
Both links are to web based mail systems and unlike POP3 mail do not download to your computer, as such they are definitively 'preview'. The wanadoo link also permits you to read Freeserve and Wanadoo mail as web mail from any PC.