In its various incarnations, Qualcomm's Eudora is probably the most popular stand-alone e-mail program. With Eudora Pro, you can test messages for complex conditions--for example, "To: contains `Smith' and `widget' appears in `Body.'? If a message matches the condition, you can automate up to five actions. For example, when a specific type of message arrives, your computer can notify you audibly, notify someone else or launch an application: If, say, an order arrives via e-mail, you might want a word processing program to launch so you can print a form letter acknowledging receipt.
Eudora Pro sells for $39. Qualcomm also offers Eudora Light for free; this program might be the right pick if you like Eudora's style but don't need its advanced features. Visit http://www.eudora.com
Still not sure what you want? You can download many free or or low-cost programs from Tucows (http://www.tucows.com). Or do a little more research on your own: To peruse the "Top Ten E-Mail Programs and Utilities," go to http://www.pcworld.com/news/daily/data/0198/980123142637.html