Is there a way to find out how Edge sends e-mail to the outside world? Let's say I send 50 e-mails at once. Does Edge send them all at once? Is there any order? Thanks.

What does it mean to send "50 emails at once"? Do you mean a single email with 50 recipients? Or do you mean 50 independent messages? If the later, that's not really at once, is it? Messages are queued in the order they are received with the exception of the priority queuing logic as described here: Understanding Priority Queuing Mike Crowley Check out My Blog!

I meant to say 50 recipients. Thanks.

let's say there were 50 recipients, but when grouped together, only 5 unique domains (10 recipients at each domain): In this case, the email would go into transport and queues would be created for each of the 5 target domains. Transport would attempt to connect to each domain one time. In the "rcpt to" section of the session, 10 recipients would be listed. this means only 5 remote connections would actually be made to deliver the 50 messages. Mike Crowley Check out My Blog!

When the sending server initiates the connection and the other server responds back, is this captured in the smtp logs of both edge and hub?

It's captured in the protocol log of the outtermost transport server. Mike Crowley Check out My Blog!