> Do I need to be concerned about this log messages in /var/log/maillog? > smtpd[43176]: ecd860f40cdb2d36 smtp cert-check result="no certificate > presented”
It depends. Based on the amount of information you gave, there are two possibilities. A connection from an MUA (ie. thunderbird) to the MTA (opensmtpd) is not encrypted, or the connection to another MTA, because it didn't present a certificate. You can further inspect with smtpctl log verbose or smtpctl trace smtp/mta. With show message or show envelope you can display the contents of the concerning message. (https://man.openbsd.org/smtpctl)
