Mailbox in CAS Server Exchange 2013

Patricia Restrepo
Patricia Restrepo used Ask the Experts™
Hello Exchange Experts,

I have 2 CAS Servers with NLB, This servers only are used as CAS server, but they have the mailbox role installed, and I have readed that in this version is not possible to remove the mailbox role once you have it installed. In this way, I would like to know what should I do. The arbitration mailbox of this servers and the database generated from this role should be removed or moved to another server?

Thanks for your suggest.

Best regards,

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yes, you can remove an individual role from Exchange 2013, you will have to uninstall the full exchange server and then can reinstall the specific role, the best if you install new fresh CAS role and then decommission these servers with muti-role.

and yes you would need to move the Arbitration System mailboxes, run the below cmd to get the info of the system mailboxes.

Get-Mailbox -Arbitration | FL Name, Database, ServerName, AdminDisplayVersion

find the info on how to move them.
Senior Systems Admin
Top Expert 2010
I assume you have this set up like this to act as load balancing for a DAG that exists on other mailbox servers? Separating roles in Exchange 2013 isn't recommended, just so you know, and the licensing cost for splitting the roles so you can use Windows NLB is actually more than the cost of an entry-level Kemp load balancer, so this kind of design isn't the best way to do things...

That said, you can keep the Mailbox role on those servers without impacting anything. Move the arbitration mailboxes off the databases by running
get-mailboxdatabase <database name> | get-mailbox -arbitration | new-moverequest -targetdatabase <database on your other Mailbox servers>

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Once that's done, dismount the databases and delete them from Exchange. You can then delete the files.

The CAS role in Exchange 2013 is little more than a reverse proxy. All the actual work of presenting client access is done by the Mailbox server holding the users' mailboxes. If there is a mailbox role on the CAS servers, and you've already spent the money for licenses and don't want to spend more for a hardware load balancer, just leave the mailbox roles on the CAS servers with the databases dismounted or deleted and you'll have no issues moving forward.


Thank you very much for your help!

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