Exchange – Slow Mailbox Migration?

KB ID 0001327 Dtd 13/07/17


I had a problem recently during an Exchange 2007 to 2013 migration, (client can’t support 2016 yet!) Where the mailbox migrations were taking ages. 


1. Disable Microsoft Replication Service Throttling

On the ‘Target’ server > Open ‘regedit’ > Navigate to;

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\MSExchange ResourceHealth

Locate the MRS REG_DWORD Value and change it to 0 (Zero)

Disable Throttling Mailbox Moves

Note: This wont take effect until the service is restarted, but don’t do that yet.

2. Change Microsoft Replication Service Defaults

Edit the MsExchangeMailboxReplication.exe.config file, you will find  it at the following location;

{Drive-Letter}:\ProgramFiles\Microsoft\Exchange Server\V15\Bin

Note: Run Notepad as administrator, or it might not let you save the changes!

Change the following settings;




Mailbox Migration Slow

Below the line (above,) add the following (only if target is Exchange 2013 SP1 (Thats CU4!) and above);


Exchange Mailbox Migration Slow

Change the following to 20 minutes;

DataImportTimeout=”00:20:00 />

Exchange Mailbox Migration Very Slow

Save and close the file.

Note: This wont take effect until the service is restarted, but don’t do that yet.

3. Disable Indexing on the ‘Target’ Database

Execute the following command;

Set-MailboxDatabase “Target-Database-Name” -IndexEnabled:$False

4. Restart the Mailbox Replication Service

Mailbox Migration Replication Restart

Can I Restart the Mailbox Replication Service While Migrating Mailboxes?

For safety reasons I would say no, but yes you can actually restart the service during a migration, the individual moves then get flagged as;


Mailbox Migration StalledDueToMailboxLock

I simply left it for a while, and they all reverted back to ‘Copying Messages’.


When you have finished remember to re-enable indexing and throttling on the target datastore.

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Author: PeteLong

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  1. does it apply to 2016? I don’t see regkey with that name in exch2016. Can you advise the steps we can do on exchange 2016 server? I see slow mailbox move from 2010 to 2016.

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    • 2016 is a little better designed, I’ve not had a problem with 2016 that warranted me changing anything?

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