Two different servers? Please explain how they are different.

Mail server is a mail server, it can send, receive emails.

 

Exchange is a Microsoft 's protocol to exchange email but also to share calendar and so on. Exchange is proprietary of Microsoft.

Not really telling me why they are on two different servers. Would an Outlook email have to go from the Exchange server to the email server to be sent out of the network to an external recipient?

no idea because usually when you have exchange you don't need a second mail server.

 

I don't understand your scenario, anyway if you have exchange and another mail server is because you want use outlook for calendar or mobile devices but not for email. (no idea why you do this).

 

Exchange can send emails without another server, so once again, no idea why you should have a dedicated mail server when you already have exchange.