I have wrote many articles  about the Exchange Hybrid process. There are lots of excellent articles on line about this process. This blog post is aimed it simplifying the whole process and ensuring 2010 clients can still connect when using Exchange 2016 servers for autodiscover.

The Exchange Online Hybrid wizard has greatly improved over the years and the Exchange Hybrid Modern Agent is an amazing step forward and provides a mechanism to quickly migrate mailboxes to Exchange Online.

Exchange 2010  support will Expire in October 2020. I have recently been performing a lot of Hybrid migrations using Exchange 2010 and Exchange 2016 as the hybrid server

I always use this powershell SCRIPT to install the pre-requisites for each new Exchange server.

Autodiscover services are typically  transferred from the Exchange 2010 servers to Exchange 2016 servers.

Simply updating the autodiscover.consto.com A record to point at the new Hybrid server and expecting clients to connect without any issues is a big mistake.

If the Exchange 2010 organisation has a load balanced virtual ip , this IP cannot be simply reused for the Exchange 2016 server. The main reason for this is that,mapi has transitioned to mapi over http from Exchange 2013 versions and higher.

Exchange 2016 has different virtual directories and also has health check urls per Exchange virtual directory.

• Kemp – Kemp have templates for Exchange 2016
• F5 – Have templates for Exchange 2016
• Netscaler – Follow this article to load balance Exchange 2016 via Netscaler HERE

When the Exchange Hybrid has been installed and configured , Run this SCRIPT
And set all of the virtual directories to your corporate domain eg. autodiscover.contoso.com

On the Exchange 2010 server , get an inventory of databases hosted on the Exchange 2010 servers. And then run this command to set the rpc client access server per Exchange 2010 database,

Set-MailboxDatabase –Identity “<Database Name>” –RPCClientAccessServer “exch2010-01.contoso.local”

This is the most important task, Exchange 2016 receives autodiscover requests and proxies them to the Exchange 2010 client access servers for mailboxes that are still hosted on Exchange 2010.

Now is the time to update the two DNS records autodiscover.contoso.com and mail.contoso.com to point to the new Hybrid server.

Exchange Online users that have been migrated and are working outside of their company offices will query the public autodiscover.contoso.com record which will point to the hybrid server, the hybrid server will respond with the correct autodiscover xml via http redirect to Exchange Online.