Cross Forrest Mailbox migration

It will be easy to use 3rd party softwares and migrate from forest A Exchange to Forest B exchange.

Can you explain what your client's requirement?
Maybe we can propose something better.

You need to have two way trust between forests and add the Target Exchange organization .

Taking out PST also take out the X500 address of mailboxes and add them back in the new mailboxes on migrated forest..

You're going to have to upgrade your 2013 server to 2016.  Unless you want to test your upper limit of frustration don't try to migrate using .pst files.  Since the mailboxes all live in a separate forest there is no need for legacyExchangeDn / X500 addresses either.  The challenge you'll face is password and SID history both of which are accounted for in the ADMT (Active Directory Migration Tool); however, it's not really appropriate in this instance since the AD users and mailboxes are already established in the target.  If flipping the migration from 2013 to 2016 isn't an option you'll most likely want to shell out the $9.99 per mailbox for Migration Wiz, otherwise the next best option I can think of is introducing a third forest (similar to a resource forest) to facilitate the unique position you're in.  I'm happy to help if you need a hand.

Have you tried below command:

New-moverequest -identity "" -BadItemLimit 100 -AcceptLargeDataLoss

Modify the baditemlimit as per your needs.

Provide the complete error information. Incomplete information will not lead to solution.

You can remove or colour the sensitive information in the error liek domain name and all.

1. Have you tried moving one or two mailboxes by themselves?

Can you move a single small mailbox over?

If yes, it may be a matter of mailbox size and this post may help:

http://social.technet.microsoft.com/Forums/en-US/exchangesvrmigration/thread/279bac54-f7bd-4d5e-884e-6c8701db13cc



2. Try modifying MSExchangeMailboxReplication.exe.config on the target CA server as follows:-

              binding name="MrsProxyClientBinding"
                 receiveTimeout="00:00:50"
                 sendTimeout="00:00:50">
          <reliableSession ordered="true" />
          <textMessageEncoding>
            <readerQuotas maxArrayLength="3048576"
                          maxStringContentLength="3048576" />
          </textMessageEncoding>
          <httpsTransport authenticationScheme="Negotiate"
                          maxReceivedMessageSize="3048576"
                          allowCookies="true" />

You are most welcome...Glad to hear your issue was resolved.