I've been using Netscape almost exclusively for the last few months, since the big problems with IE surfaced, even though Microsoft has released patches & fixes and so forth, and have had no problems with Ebay, Mudcat, Hotmail, or my usual mail (through my local ISP).

My local ISP DOES filter bulk mail, though, so I would also recommend that you contact your local server to see if they do this, as they can mistake mail from someone you do want to do business with for junk (which is just logical - how can a machine differentiate between bulk mail that you want and bulk mail that you don't want?) - you should be able to tell them specific groups from which it is all right to let mail through.