Migrate SharePoint Users from One Domain To Another

Requirement:
During a acquisition, Our company decided to merge with an acquired company's AD by re-creating their user Ids in our AD. Also, the acquired company had a bunch SharePoint sites and we wanted to migrate them to our SharePoint environment.

That brought an another challenge of re-mapping user Ids with permission between domains. How do we migrate SharePoint users from one domain to another domain?

Solution: 
Well, In SharePoint 2007 days, I used STSADM to migrate users between domains:
Stsadm -o migrateuser -oldlogin domain\OldUserID -newlogin domain\NewUserID -ignoresidhistory 

Now with SharePoint 2013, Its replaced with the PowerShell cmdlet: Move-SPUser. So, rather moving users one by one, we prepared a CSV file, mapping users from one domain to new domain and used PowerShell script to migrate users in bulk.

Here is my CSV file structure:

The csv file just maps old SAMAccountName with the new one.

PowerShell script to Migrate Users from one domain to another:

Add-PSSnapin Microsoft.SharePoint.PowerShell

#Import data from CSV file
$UserData = Import-CSV -path "C:\Accounts.csv"

#Iterate through each Row in the CSV
foreach ($Row in $UserData)
 {
    write-host "Processing user:" $row.Email

    #Site collection URL
    $siteURL ="https://intranet.crescent.com"
    $site = Get-SPSite $siteURL

    foreach($web in $site.AllWebs)
     {
        #Get All Users
        $UserColl = Get-SPUser -web $web.Url

        foreach ($User in $UserColl)
        {
            #Get values from CSV File
            $OldUserID= $Row.OldUserID.Trim()
            $NewUserID =$Row.NewUserID.Trim()
            $Email = $Row.Email.Trim()

            #Search for Old User Accounts
            if($User.UserLogin.Contains($OldUserID))
             {
                #Update the User E-mail
                Set-SPUser -Identity $User.UserLogin -Email $Email -Web $web.URL

                $NewUser = $User.UserLogin.replace($OldUserID, $NewUserID)

                #Migrate user from Old account to new account - migrate users to new domain
                Move-SPUser -Identity $User -NewAlias $NewUser -IgnoreSID -confirm:$false
                write-host "User Migrated: $($User.userlogin) at site $($web.Url)"
             }        

        } 
    }
}

This PowerShell script migrates users to new domain programmatically. You have to use the same method when users leaves the company and rejoin - if their AD accounts are deleted and re-created.