I have my first Exchange 2013 server up and running for quite a while and it is running great.  I had the need for a second Exchange server 2013, so I installed it and all is fine.  Our company plans have now changed and I need to remove the newly added Exchange server.  I do NOT want to affect the main server.  Can anyone tell me how to safely remove the second exchange server?  When I try from Add and Remove programs, I get the following error:Error:
Uninstall can't continue. Errors:

This mailbox database contains one or more mailboxes, mailbox plans, archive mailboxes, public folder mailboxes or arbitration mailboxes. To get a list of all mailboxes in this database, run the command Get-Mailbox -Database <Database ID>. To get a list of all mailbox plans in this database, run the command Get-MailboxPlan. To get a list of archive mailboxes in this database, run the command Get-Mailbox -Database <Database ID> -Archive. To get a list of all public folder mailboxes in this database, run the command Get-Mailbox -Database <Database ID> -PublicFolder. To get a list of all arbitration mailboxes in this database, run the command Get-Mailbox -Database <Database ID> -Arbitration. To disable a non-arbitration mailbox so that you can delete the mailbox database, run the command Disable-Mailbox <Mailbox ID>. To disable an archive mailbox so you can delete the mailbox database, run the command Disable-Mailbox <Mailbox ID> -Archive. To disable a public folder mailbox so that you can delete the mailbox database, run the command Disable-Mailbox <Mailbox ID> -PublicFolder. Arbitration mailboxes should be moved to another server; to do this, run the command New-MoveRequest <parameters>. If this is the last server in the organization, run the command Disable-Mailbox <Mailbox ID> -Arbitration -DisableLastArbitrationMailboxAllowed to disable the arbitration mailbox. Mailbox plans should be moved to another server; to do this, run the command Set-MailboxPlan <MailboxPlan ID> -Database <Database ID>.

Warning:
There are messages waiting in the following queues: "EXCHANGE2\3", "EXCHANGE2\4". If you proceed with the removal of Exchange Server, data loss may result.
For more information, visit: http://technet.microsoft.com/library(EXCHG.150)/ms.exch.setupreadiness.MessagesInQueue.aspx

TIA,

There are a number of hidden mailboxes that need to be moved/removed. Take a look at this and see if it helps:

• http://fieldnotes.conexion.ca/2013/07/exchange-2013-hidden-mailboxes.html

There's also the arbitration switch so all in all, cmdlets are below:

Get-Mailbox -Server RetiringServer | New-MoveRequest -TargetDatabase DBonNewServer

Get-Mailbox -Server RetiringServer -Archive | New-MoveRequest -TargetDatabase DBonNewServer

Get-Mailbox -Server RetiringServer -Arbitration | New-MoveRequest -TargetDatabase DBonNewServer

Once done, you should be able to decommission it. 

Thanks.

Hi,

We need move all mailbox, public folder to another Exchange server, also include archive, arbitration mailbox.

I find an similar thread about your question, for your reference: https://social.technet.microsoft.com/Forums/exchange/en-US/4726db53-b5ac-488a-a801-a4774ffcdc34/cannot-uninstall-exchange-2013?forum=exchangesvrgeneral

Besides, please move message to another message queue server before uninstall Exchange server. Please refer to:
https://technet.microsoft.com/en-us/library/cc753436.aspx