Exchange MTA queue

I have two servers in one exchange site. I recently installed internet mail service on new server (i’m gradually trying to phase old server out). I checked both MTA queues today and in the old servers MTA queue there are like 49 MTA errors. I cansend test mails to work from home and they come across okay, however what is this 49 MTA messages? They aren’t error messages like I have seen when mail is jammed in queue – where i can see who sender or recipient is. Thanks!