To be used with the output of the Get-PnPProvisioningTemplate cmdlet, this script will replace all mail addresses (user accounts) in the xml file of the output with one static mail address. This is useful, when also content (pages) need to be moved to another tenant.

ReplaceMailAddresses.ps1

param (
    $InFile,
    $OutFile,
    $MailDomain,
    $ReplaceWith
)

$regexFind = "\b[A-Z0-9._%+-]+@$MailDomain\b"

$inputContent = Get-Content $InFile
$lineCount = $inputContent.Length

$outputContent = $inputContent

for ($i = 0; $i -lt $lineCount; $i++)
{
    if (($inputContent[$i] -match $regexFind) -eq $true)
    {
        $outputContent[$i] = $inputContent[$i] -replace $regexFind, $ReplaceWith
    }
}

$outputContent | Out-File $OutFile