MailWasher Pro works with virtually any e-mail software, and it's configurable. You can create customized filters, such as blacklists and whitelists, for identifying spam. The software learns from you, so it gets smarter over time, and it does basic virus scanning too. You can also read mail within the program, so it works as a kind of mini e-mail client.
Download MailWasher Pro | Price: Free
EPrompter: Since so many free Web-based e-mail programs (including Gmail, Yahoo Mail and others) are available, many people use multiple accounts. That's certainly useful, but it's a pain as well. Manually checking each account a couple times a day is a productivity killer if there ever was one.
EPrompter solves the problem neatly. It automatically checks all of your Web-based e-mail every 15 minutes and alerts you when you have new messages. You can have it monitor up to 16 different accounts. You don't even have to log into the different Web-based mail systems to see your inbox, read your messages and respond to them -- you can do all of that from directly within the program. You can delete mail, as well.
I had problems getting Hotmail to work with this software. If I identified it as Live Mail, it worked, but another time it wouldn't. But ePrompter is free, and it works fine with other Web-based mail services, so it's certainly worth a try.
Download ePrompter | Price: Free
POP Peeper: Here's a great tool for checking all of your e-mail accounts, whether they're Web-based (like Gmail) or POP 3 accounts (common among e-mail providers). It works with just about any Web-based mail service or ISP, including Gmail, Hotmail, Juno, Yahoo Mail and many others.
After a brief setup procedure for each account, POP Peeper checks your mail regularly and alerts you when new mail comes in. You can get video and audio alerts, and customize different sounds for each of your accounts. The utility is small enough to use as portable software -- just install it on a USB thumb drive and carry it with you.
And it does more than just notify you when new mail comes in: You can read, create, and delete mail inside it, too. You can even send or open file attachments with it.
Download POP Peeper | Price: Free