First, I offer my hearty thanks to Fayland for providing this fork, which is basically just bug fixes for Net::SMTP::TLS. For that, I offer a hearty 5 stars.
The problem with this module is its legacy of Net::SMTP::TLS, which in many important ways, does not behave at all like Net::SMTP. If you are seeking a robust and mature Net::SMTP implementation that adds STARTTLS, look to Net::SMTPS instead. The author of Net::SMTPS wrote it the right way, as a very thin subclass of Net::SMTP, so that it benefits from the very well maintained, mature, and robust Net::SMTP module.