Yes, thE TLS information is missing from the SMTP log file, even when logging is set to Detailed.
For inbound traffic, I run Declude with LogLevel=Debug. This causes all of the Received header records from a message to be included in the log file. I parse the logs into a SQL database and then filter for the Received entries which include "BY <myservername>". This allows me to identify senders by encryption status, encryption version, and ciphersuite. Certficate verification is a client issue, so it is unknowable for incoming connections.
For Outgoing messages, it gets trickier . You would still need Declude to capture the TLS information. But you would also need the SmarterMail SMTP log (probably Detailed setting). The SmarterMail log will have an entry for any certificate which does not verify.
Of course, a purpose-built solution is preferable to text parsing.