Blesta 5.9 - the last one. Server has SSL cert, sure. It self-signed, but valid. I can connect to the server with MUA and receive/send emails from my PC. But to do that if I configure the Mail-account for the first time I have to confirm the storing of SSL cert on PC first.
Telnet don't respond on 465 (because cannot connect through SSL I think) if I close connection I see in logs on server: An unexpected TLS packet was received
Telnet on 587 respond, I see HELO message from server.
If I try to send test mail from admin panel, as before, (url /admin/settings/company/emails/mail/) I see in logs on mail server:
TLS error on connection from HOST-WITH-BLESTA (gnutls_handshake): Decryption has failed.