As part of migrating from Exchange 2010 to Exchange 2016, our customer will also be moving to implementing split DNS (going from "domain.local" with a certificate issued by an internal CA to "domain.com" with a certificate issued by a 3rd party CA). Is anyone able to provide some advice on doing this in a way that minimises the impacts to clients, and also provide some information on what the impact to clients we may experience when performing this change.
Normally you would have to reduce the TTL of DNS resources records in question when changing IP-adresses or host names. But as you are changing the namespace, the clients would have to pickup the new urls provided by AutoDiscover. AutoDiscover caches the data requested for a single user. So a change in vDir url configuration will be picked up by clients immediately.
For Exchange 2010, restart the AutoD application pool
For Exchange 2013+ you can use the follow two one-liners to restart the AutoD application and the service.