openssl s_client -connect imap.example.com:993

Category: Mail Servers & Postfix

openssl s_client -connect imap.example.com:993

Check TLS on the IMAPS port

Verifies the certificate presented on the implicit-TLS IMAP port 993, used by most mail clients. Check the validity dates and that the hostname matches the certificate. Related: port 143 uses STARTTLS instead of immediate encryption.
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