Testing Mail Server SSL

PUBLISHED ON 12/02/2019 — SERVERS

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
TAGS: IMAP, MAIL, SMTP, SSL