I would suggest you use something like [email protected]. Perhaps you could do a separate e-mail just for hiring. Say your email is [email protected], do a [email protected] just for hiring. That way, you can just auto-forward to someone else when you need him to take over. Here's a reason why I think this would also benefit your hiring a bit. I usually address my emails with the name of the person, so I'd open with "Hi John", "Hey John", "Dear John", or some variation of that. I can't do that at [email protected], because there may be multiple people reading that, so I'd have to do something more generic. What that means for you, the employer, is that I actually read your post and wrote the e-mail, and not just bcc'd you together with another hundred guys.

I'd never think sending feedback would be a bad choice. Of course, don't send something offensive like "you're the worst programmer ever". I don't think anyone would be offended by "we're looking for someone with more experience in X", which is what I suggested.

As for the way I phrase some of my emails: I've only send the "is the job still available" kind only a couple of times, but perhaps surprisingly I got some of the best contacts this way. Perhaps because the guy on the other end was open to going past that. In fact, the best hiring process I've had with someone I had emailed with "I've attached my resume" when in fact I hadn't. Few jokes later, I had a job offer.