I only changed my script to use Net::SMTPS module and the email was sent because it ignored the original SSL option in the new method and used a standard connection. Then I added the doSSL option and the script failed with a certificate error:

It's strange, because using Net::SMTP there was no certificate error as it authenticated through SSL, accepted the mail header and body, but it did not finished the connection (sending the "." after the body).

BTW, in the meantime, I tried to use Email::Sender::Simple which I used in another project some years ago, and now it also failed with a timeout. I checked, and it uses Net::SMTP methods!!!