While troubleshooting a failed mailbox move to Office 365 for a customer, I was surprised to see that the basics was not covered – to enable the MRS Proxy!
MRS Proxy is required for cross forest mailbox moves – be it between two Exchange forests or Exchange on-premise to Exchange online.
The 2013 CAS server is responsible for proxying the incoming move requests from the other forest to the mailbox server. The ability of the CAS server to accept incoming move requests is disabled by default, which means that MRS Proxy is turned off.
Turning on MRS Proxy is really simple and can be done from both the EAC and Shell. It is much easier using Shell, I must admit.
Get-WebservicesVirtualDirectory –Server <servername> | Set-WebServicesVirtualDirectory –MRSProxyEnabled $true
If you have more than one CAS 2013 server, the proxy has to be enabled on all of them.
Get-WebservicesVirtualDirectory | Set-WebServicesVirtualDirectory –MRSProxyEnabled $true
If you want to use the EAC, navigate to Servers –> Virtual Directories –> EWS (Default Web Site).
Click the Edit button and check the “MRS Proxy Enabled” option.
It is important to know which CAS servers need the MRS proxy enabled – whether the ones in the source or target forest. If the mailbox move is initiated from the target forest (pull move), the MRS proxy should be enabled on the source CAS servers and if the move is initiated from the source forest (push move), the proxy should be enabled on the CAS servers in the target forest.
While on-boarding and off-boarding to/from Office 365, the proxy should always be enabled on the on-premise CAS servers. Well, you can’t play with Microsoft’s servers ;)