Can you tell exactly what computer a message came from?

Answer 1

According to Ken Hollis and the alt.spam FAQ: You cannot generally tell by a e-mail header which specific computer the e-mail came from. Just about every time you dial into your ISP (internet Service Provider) you are assigned a different IP address. If someone sends you an e-mail and they log out, the next time they log in their IP address will most likely be different. If the computer has a permanently assigned IP address *and* you have the cooperation of whomever owns that block of IP addresses you *might* be able to get information on who might have sent the e-mail. About the only way to tell *exactly* which e-mail account the e-mail was sent from is to get the ISP (Internet Service Provider) to tell you. Usually the ISP will require you to get the local police involved (a warrant of some type) to force the ISP to give you that information. Even given that you know the account the e-mail originated from, a forger can find out that person's account / password and log in as them, they can gain access to that computer while the person who owns that computer is away from the computer or they could install a back door program that allows them to control that person's computer remotely. If this were to happen then the forger could send the e-mail and nobody would know who *specifically* sent the e-mail.