# Connect to Exchange Online
$credential = Get-Credential
Connect-ExchangeOnline -Credential $credential

# Define the source and target domain
$sourceDomain = "olddomain.com"
$targetDomain = "newdomain.com"

# Prompt for user input to specify a single user
$userEmailAddress = Read-Host "Enter the email address of the user to update"

# Get the specified user
$user = Get-Mailbox -Identity $userEmailAddress

# Check if the user exists and if their email address matches the source domain
if ($user -ne $null -and $user.PrimarySmtpAddress -like "*@$sourceDomain") {
    $currentPrimary = $user.PrimarySmtpAddress.ToString()
    $newPrimary = $currentPrimary.Replace($sourceDomain, $targetDomain)
    
    # Confirm the update with the user
    Write-Host "Updating primary email address for user: $($user.DisplayName)"
    Write-Host "Current email address: $($user.PrimarySmtpAddress)"
    Write-Host "New email address: $newPrimary"
    
    $confirmation = Read-Host "Do you want to proceed with the update? (Y/N)"
    if ($confirmation -eq "Y") {
        # Change the email address for the user
        Set-Mailbox -Identity $userEmailAddress -PrimarySmtpAddress $newPrimary
        Write-Host "Primary email address updated successfully."
    }
    else {
        Write-Host "Update canceled."
    }
}
else {
    Write-Host "User not found or their email address doesn't match the source domain."
}

# Disconnect from Exchange Online
Disconnect-ExchangeOnline