http://technet.microsoft.com/en-us/library/dd638206(v=exchg.150).aspx
Use Setup /m:RecoverServer to recover a server
✑ Retrieve any replay lag or truncation lag settings for any mailbox database copies that exist on the server being recovered by using the Get-MailboxDatabase cmdlet.
✑ (Box 1) Remove any mailbox database copies that exist on the server being recovered by using the Remove-MailboxDatabaseCopy cmdlet.
✑ (Box 1) Remove the failed server's configuration from the DAG by using the Remove-DatabaseAvailabilityGroupServercmdlet.
✑ Reset the server's computer account in Active Directory. For detailed steps, see Reset a Computer Account.
✑ (Box 2) Open a Command Prompt window. Using the original Setup media, run the following command: Setup /m:RecoverServer
✑ (Box 3) When the Setup recovery process is complete, add the recovered server to the DAG by using the Add-DatabaseAvailabilityGroupServercmdlet.
✑ (Box 3) After the server has been added back to the DAG, you can reconfigure mailbox database copies by using the Add-MailboxDatabaseCopycmdlet.
* You can recover a lost server by using the Setup /m:RecoverServer switch in Microsoft Exchange Server 2013. Most of the settings for a computer running
Exchange 2013 are stored in Active Directory. The /m:RecoverServer switch rebuilds an Exchange server with the same name by using the settings and other information stored in Active Directory.
References:
Recover a Database Availability Group Member Server
Recover a Database Availability Group Member Server: Exchange 2013 Help
