Through the use of RecoverServer we can recover Exchange servers by restoring system state. The trick is to recreate the server and trick AD into believing it is the same computer. Note, nothing does the trick like having the same hardware performing the recovery otherwise you can imagine how AD might get confused. Try to replicate it to the letter, including the drives (size and letters).

We will use RecoverServer switch on same hardware or different hardware which is configured with the same name as the one which has crashed or is permanently down for any reasons, setup will read the configuration information from the Active Directory and recreate your Exchange installation based on that. Be sure your mailbox files are set up in the exact same route, etc.

Prerequisites:

• This scenario will apply for HubTransport, MailBox, ClientAccess and management tool. The RecoverServer switch cannot be used to recover an Exchange Edge Transport Server.
• The server on which recovery is being performed must be running the same operating system as the lost server. For example, you can’t recover a server that was running Exchange 2010 and Windows Server 2012 on a server running Windows Server 2012 R2, or vice versa.
• The same disk drive letters on the failed server for mounted databases must exist on the server on which you’re running recovery. The server on which recovery is being performed should have the same performance characteristics and hardware configuration as the lost server.

Now recover lost exchange server :

• Reset the computer account to do this, Log on to a respective Domain controller and run “dsa.msc” command to open Active Directory Users and Computers MMC snap-in > select computer> in right pane select a crashed computer name > Action> Reset Account.
• Join system to the respective Domain.
• Install Exchange server dependencies
• If Exchange is installed in a location that is not the default location, use the /TargetDir switch to specify the location of the Exchange binary files. If you do not use the /TargetDir switch, the Exchange files are installed in the default location (%programfiles%MicrosoftExchange ServerV14).
  To determine the installation location of Exchange, follow these steps:

Open ADSIEDIT.MSC or LDP.EXE.

Expand the following location: CN=ExServerName,CN=Servers,CN=First Administrative Group,CN=Administrative Groups,CN=ExOrg Name,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=DomainName,CN=Com

Right-click the Exchange server object, and then click Properties.

Locate and open the msExchInstallPath attribute, which stores the current installation path.

• Now install exchange server to do so change to the location containing your Exchange 2007 Setup files, then type Setup.com /M:RecoverServer. (If u r going to recover only Hub transport role because older system was installed only HubTransport Role, Use recoverServer switch followed by the “/DoNotStartTransport” syntax to stop exchange transport service.)

• A recovered server with the Mailbox Server role must have the respective Mailbox and Public folder database restored from backup, or copied back from the disks on the old server (if possible). If the Public folders are replicated with other Exchange servers in the Exchange organization, you don’t need to restore it as an empty Public Folder database will be backfilled from the other Public folder server(s).
• If you restore HubTransport role you also need to restore saved message queue databases (which in Exchange 2007 are stored in an ESE database and not in the NTFS file system as was the case with Exchange 2000 and 2003) and place them in the right folder.