MailWasher allows you to preview multiple accounts and all aspects of your e-mails before you download them. It also allows you to delete and bounce e-mails back to the originator. The sender will receive an e-mail saying the address was unknown. Another feature helps identify and mark e-mail as normal, virus, possibly virus, possibly spam, probably spam, chain letter, and blacklisted, so you can deal with the e-mail as you wish. Other features are comprehensive customizable filters, use of MAPS RBL to identify spammers, multiple accounts, visual and auditory notification of new e-mail, minimization to system tray, and much more. It is compatible with POP3 servers.
Limitations: Will only monitor one email account. A Pro Version is available without restrictions.