MS Exchange 2016 isn't receiving incoming e-mail...

I recently installed Exchange 2016 Standard on a clean Windows 2012 R2 VM install.  
1st:  Installed Win 2012 R2
2. Installed all applicable Win updates
3. Installed the AD Role
4. Promoted to a DC (corp.domain.com) and created necessary user accounts
5. (NOTE)  Hardware firewall router had been previously configured and working on a WIn 2012 R2 with Exchange 2013 successfully.
6. After number 4, installed more critical updates.
7.  Installed Exchange 2016 Standard and restarted VM
8.  Logged into the https://dc-srv/ecp and applied settings on the Exchange 2016 server similar to those of Exchange 2013 (ie... Accepted Domain(s), established user accounts and chose to allow e-mail from Anyone (mail flow), established the default send connector and restarted the VM server to refresh the entire server again.
9. (NOTE)  DNS settings are similar to those of the Exchange 2013 server and therefore, not many changes were necessary but yet, were applied where applicable to the new Exchange 2016 server.

Tested e-mail to the Exchange 2016 server from a gmail, yahoo, and a live account and the new Exchange 2016 e-mail server isn't accepting incoming e-mail.
NOTE:  It is able to send out e-mail successfully but, isn't receiving replies.
Lastly, the e-mail messages are not bouncing back to gmail, yahoo and Live test e-mails.

Any ideas as to what may be preventing e-mail from being received?  A new configuration change different from that of Exchange 2013 necessary to have the Exchange 2016 server working?