An email has at least three fields that can both influence the address to which a reply goes and isn't necessarily visible to the recipient's MUA. Even if the

An email has at least three fields that can both influence the address to which a reply goes and isn't necessarily visible to the recipient's MUA. Even if the recipient where to look into the headers, there are plenty of games to play with deceptively constructed international domain names. There is also the social engineering aspect I mentioned.