$import= import-csv -Path ‘\email-list.csv’ #location of CSV file
$import | ForEach-Object {
$stringSignature = get-MailboxMessageConfiguration -Identity $_.identity.trim() | fl signatureHTML
$string = $stringSignature | Out-String #to convert to string....
$string = $string -replace "logo.png", "newlogo.png"
if($string -like 'maharjanrajan.com') { #to check if the stringg exists
$string = $string -replace "maharjanrajan.com", "rajanmaharjan.com"
}
$string = $string -replace "SignatureHtml : ", "" #to replace the word SignatureHtml : which comes when converting to string from above
$string = $string -replace '<div></div>', '' #replace unnecessary open close of div without content
Set-MailboxMessageConfiguration -Identity $_.identity.trim() -DefaultFontName 'Arial' -AutoAddSignature $true -AutoAddSignatureOnReply $true -SignatureHtml $string
Write-host $_.identity 'Signature Modified'
}