SSL_accept error when mail client connect to postfix

Port 465 is for SMTPS, it uses SSL immediately when establishing the connection and then uses the same SMTP protocol as normally found on port 25 after the secure connection is established. You test from the commandline with:

openssl s_client -connect

Using telnet to connect to port 465 will result in an error message in the log files because the SSL protocol isn't used.

Just for completeness: to test TLS on the normal SMTP port, TCP/25

openssl s_client -starttls smtp -connect