During one of my favorite sessions in Ignite last year, Microsoft announce a new feature : Hybrid Agent displayed in the image above. The next part of this blog is step by step screenshots displaying the configuration of Hybrid Agent on two Exchange 2016 CU10 servers.
First of all run this powershell command on all Hybrid servers.
Set-WebServicesVirtualDirectory -Identity “EWS (Default Web Site)” -MRSProxyEnabled $true
Most organisations route outbound external smtp traffic via a smarthost which can normally be an appliance like Cisco Ironports and do not permit outbound port 25 traffic from Hybrid servers. I would suggest temporarily allowing smtp traffic outbound from the Hybrid servers until the Hybrid agent installation completes then block outbound port 25 again on the hybrid servers.
The next steps run through the Hybrid agent setup.
Now when attempting to migrate mailboxes note the change in the migration endpoint highlighted in the image below