How do I show a certificate's detail in OS X Mail (Lion)

Solution 1:

I'm not aware of any way to force Mail to enter the error dialog, so you'll have to get the certificate from the mail server using another tool. (mail is getting it each time it works, just not dumping it to a file or an assistant for you to peek at)

Lion uses the Keychain Access app (from /Applications/Utilities/ ) to manage certificates and view validation chains, root certificates, check validity, etc... The command line equivalent that does the work behind the pretty GUI is security.

There is some basic documentation covering evaluating ssl certificates but they assume you already understand the mechanics of Public Key Cryptography.

Here is what the Certificate Assistant looks like when evaluating Apple's Code Signing Certificate that shipped with Lion.

Solution 2:

This is not in Mail, I know of no way to do that, but this does not require any new software. In Terminal:

echo ^d|openssl s_client -connect host:port 2>/dev/null |  sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' |  openssl x509 -noout -subject -dates