Please advise. I have 1,896 bouncebacks. Should I just delete all?

I'm assuming you did a 25,000 member mailing or so, which means that roughly 7% of your email addresses are bad.

You could simply delete them if you wish, knowing that subsequent mass mailings will produce another 7% bounceback rate. Or you can go into each record, look at the reason for the bounceback, and update the Classmate's email address whenever possible. I realize that's a big chore, but then, if you're running an alumni site with 25,000 members, a 7% bouce rate is really rather typical. Whether you're going to try to correct those email addresses or not is really entirely your call.

We only have 6,280 emails of which we have 2,179 profiles. Some of the ones coming back are from profiles. I know that the old ones are suspect. If someone does not have a profile and has a bounce back I will get around to deleting. The ones I am concerned about are the ones that I know have a profile created. You answered my question that I will have to check it one. OK. Next big project!