Does Anyone know how to increase that? It seems like its moving only two mailboxes at the same time and its terrible slow.

source server is exchange 2010 and the number there of simultaneous moverequest has already been increased per "MsExchangeMailboxReplication.exe.config".

i tried the same in the target exchange 2013 server but it already has higher values as you can see:

C:\Program Files\Microsoft\Exchange Server\V15\Bin\MsExchangeMailboxReplication.exe.config

 <MRSConfiguration
    MaxRetries="60"
    MaxCleanupRetries="480"
    MaxStallRetryPeriod="00:15:00"
    RetryDelay="00:00:10"
    MaxMoveHistoryLength="5"
    MaxActiveMovesPerSourceMDB="20"
    MaxActiveMovesPerTargetMDB="20"
    MaxActiveMovesPerSourceServer="100"
    MaxActiveMovesPerTargetServer="100"
    MaxTotalRequestsPerMRS="100"

thanks alot!

did u restart replication service after changing the config.

yes MSExchange Mailbox Replication Service on both machines.

but i did not increase any value on exchange 2013, i just increased the values on exchange 2010.

these are default values of exchange 2013:

    MaxActiveMovesPerSourceMDB="20"
    MaxActiveMovesPerTargetMDB="20"
    MaxActiveMovesPerSourceServer="100"
    MaxActiveMovesPerTargetServer="100"

Did you edit the config file on all 2010 CAS servers and then restart the service?

yes MSExchange Mailbox Replication Service on both machines.

but i did not increase any value on exchange 2013, i just increased the values on exchange 2010.

these are default values of exchange 2013:

    MaxActiveMovesPerSourceMDB="20"
    MaxActiveMovesPerTargetMDB="20"
    MaxActiveMovesPerSourceServer="100"
    MaxActiveMovesPerTargetServer="100"

plz increase the value on 2013 CAS boxes.

Found the Problem. The configuration on exchange 2010 and 2013 was correct. It was related to one target database.

i does move more then five mailboxes the same time now.

you do NOT have to change values on exchange 2013, its already set to 20 as default.

thanks for your help

Would you mind sharing what you found on the target database?  I'm also not able to move more than 2 mailboxes at a time after modifying the correct values in the MRS config section of C:\Program Files\Microsoft\Exchange Server\V15\Bin\MsExchangeMailboxReplication.exe.config. for both 2010 and 2013 and restarting the MSexchange Mailbox repl services. 

*Edit

It eventually started working for me.  I did a couple things.  I had also tried editing the retry times and values in the config file and had put one out of bounds (See default, min and max range values in the section above MRS config).  I corrected that value to a min range value and restarted the services.  My moves were already in progress and they didn't go right away to more than 2 instances.  But after a couple hours I came back and it had. 

The other thing I did do was enter the product key for my new Exchange box, since I hadn't done that yet.