Intro

When deploying new SSL certificates on the mail server, this is my prefered way of thesting them.

Testing

Testing the SSL certificates provided by the server can be done on any Linux, macOS, unix like machine by using openssl.

IMAP via SSL

Port: 993

# openssl s_client -showcerts -connect mail.example.com:993

POP3 via SSL

Port: 995

# openssl s_client -showcerts -connect mail.example.com:995

SMTP via SSL

Port: 465

# openssl s_client -showcerts -connect mail.example.com:465

SMTP via TLS/StartTLS

Port: 857

# openssl s_client -starttls smtp -showcerts -connect mail.example.com:587

See Also