I'd have a look in the settings to see if you have "sent a notification when read" or something similar set up.
Its been a while since i used outlook express 6, but i think there is something in the menu that can auto send a reply to the sender when you read a message, so they know you have read it.
.txt files are harmless, but if you have turn off extensions for know file types, or hide system files, then it may show up with a .txt extension. when the actual file name is file.txt.bat or sometimes file.txt ____________________________.bat where the _ are spaces.
These can cause problems if opened.
M.