Hey!
I had to disable my email servers message encryption requirement option to receive registration email. Your email server is sending unencrypted emails and my server is configured to block all messages which aren’t encrypted. Maybe you could fix the issue, unencrypted messages are from the past and shouldn’t be sent at all. I’m sure many others gave up, cause they didn’t receive any emails from your server.
Postifx option:
Had to change
smtpd_tls_security_level=encrypt
to
smtpd_tls_security_level=may
Best regards,
Ako