I've had Exchange 2010 for a long time. Got a new Exchange 2016 server recently and have a working coexistence as I'm learning the new version. One thing I've had trouble understanding, as many people have and there are tons of articles out there, is the receive connectors. On 2010, I had multiple connectors. For example, a connector on port 25 for external SMTP servers, a separate connector on port 25 for internal SMTP machines, and yet another separate connector on port 25 for internal Exchange servers. All of these connectors are for different purposes and are configured differently with incoming IPs and authentication methods. I tried doing something like this on the 2016 server and ran into issues. It appears that only one connector can exist for port 25. Whether it's for external SMTP or internal SMTP, or internal Exchange servers. All has to be combined into ONE connector?
SnapOverflow
With regards to the behaviour of Receive Connectors - nothing has changed since Exchange 2007 days. They still behave in the same way. You can have multiple connectors listening on port 25, but you need to ensure the scope is is configured correctly.
For most implementations of Exchange the default connector set is fine - I rarely have to change it. The only time I add additional connectors is for app relaying, which works in the same way as it always did. Configure the correct source IP addresses and permissions.