Please note that when you subscribe to a thread posted in a forum on this site, you will get an email message sent to you whenever someone else posts a new reply to that thread. This is ONLY a notice of that post and provides a link to take you to that thread. This also includes classified ads that people post here. DO NOT REPLY TO THIS NOTICE. It will not go to the person posting that reply as some people evidently believe.
So in the case of those people posting ads, and getting a reply to their ad, that potential customer you THINK you sent a message to has not really been sent a message at all. So they wind up thinking you are just ignoring them and probably make their purchase elsewhere.
And along that same line, if you have subscribed to a thread, or posted a classified ad, and your email address is not uptodate.... Guess what? You don't get those emails either.....