Adds VERP support to NET::SMPT

main.cf

# Add this line to your postfix main.cf file to add VERP support.

smtpd_authorized_verp_clients = $mynetworks

verp.rb

# Adding VERP support to Net::SMTP.
module Net
  class SMTP
    def mailfrom(from_addr)
      if $SAFE > 0
        raise SecurityError, 'tainted from_addr' if from_addr.tainted?
      end
      getok("MAIL FROM:<#{from_addr}> XVERP")
    end
  end
end