I have noticed the same issue with my Droid Incredible. Tech support had no idea what was causing this and thought I had a virus, so they sent me a replacement phone. Other people at Verizon thought the SD card was defective and had me reformat the card and replace it. Nothing has worked. If I don't delete all the files on the SD card every few days, the card becomes full and I receive email errors.
The solutuion I am going to try is to create a Gmail account and have my pop3 mail forwarded to it and then have Gmail sync to my phone. This way, the Token files shouldn't appear as my pop3 email will no longer push to my phone directly.