According to security experts, replying to phishing mail can be dangerous. There have been reports about spam mail, supposedly sent by old high school/college friends and whatnot, wondering what the recipient might be doing with his life, since it has been such a long time and…They miss you. Well, asking to refresh your recollection might not be a great idea, because, most probably, it will provide the sender with information, which might otherwise seem trivial and harmless, but can prove to be a powerful tool in the right (wrong) hands.
The minimum information the scammer gets assuming you replied to his email are your IP and address.
This, however, is just part of the problem: leaving personal information “out in the open” is a dangerous thing, whether it be on MySpace or in a reply to an email. “If you're going to share a lot of personal information about yourself, you have to understand that you're giving people a lot of information that they can use to further personalize their attack,” said Gary Warner, a University of Alabama at Birmingham computer forensics professor.
There is really no good way to protect yourself from these scams other than just being aware of their existence and acting accordingly to that knowledge.