Cant respool old emails, but new ones send fine?

The server mail settings were wrong for a few hours, and some emails backed up. New emails are sending fine with the settings fixed, but I cannot get the old emails back out. I keep copying files from Mail/Undeliv to Mail/Spool and they just get put right back into Undeliv. I've compared the files that aren't going to files that are going, in the short time they're in spool, and they are exactly identical, to the byte. I can so absolutely no reason for the new ones to work and the old ones not too.

Any information would be helpful, thanks!