What is MRS Proxy?

Mailbox Replication Service(MRS) Proxy which is used to enable option for Cross forest migration. It is very much required if you want to have Hybrid Exchange Forest where integrated with Exchange Online(Office 365).

This service makes your on-board and Off-Boarding of mailboxes very seamless. You need to enable MRSProxy in all the Client Access servers to make this happen. If you have not enabled MRSProxy, you will end up with the error


If you have Loadbalancer(NLB or HLB) configured for behind your CASArray, You need to enable in all the servers,

MRSProxy will be in disabled by default. That you can see in the EAC under Servers–> Virtual Directories–> EWS(Default Web Site)



How to Enable MRSProxy?

In Power Shell, Use Get-WebServicesVirtualDirectory -Server EX-2016 |fl


It is very easy to enable MRSProxy through Powershell

->use the below command to enable for single server

Set-WebServicesVirtualDirectory -MRSProxyEnabled $true

->use the below command to enable for single server

Get-WebServicesVirtualDirectory|Set-WebServicesVirtualDirectory -MRSProxyEnabled $true

By default,MRSProxyMaxConnections is 100, use below command to increase the connections

Set-WebServicesVirtualDirectory -MRSProxyMaxConnections 200

run IISRESET  once connections count increased

How to Increase MRSProxy Timeout Settings?

in your Exchange 2010, Go to the path of Exchange Installed idealy C:\Program Files\Microsoft\Exchange Server\V14\ClientAccess\exchweb\ews, You will see the web.config file.


open it in notepad and you will see the  DataImportTimeout.


You can change the Timeout settings and then do IISRESET to get this applied.

4 thoughts on “Mailbox Replication Service (MRS) Proxy”
  1. In Exchange 2016 we need to increase the DataImportTimeout for MRS Proxy, Client says he is not able to locate this file ? though is visible in one of our Exchange 2010. Any idea how can i increase the limit ?

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