My server has a DV certificate from Let's Encrypt and auto renewed by certbot cron job. Recently I ran into an issue where the auto renew and I've since manually renewed it. I can verify that it is in fact renewed now and good until Dec, 2018. However Mail is still giving me the warning that the certificate has expired and when I show details for the certificate it shows the old expiration date. Seems as though either the mail app or the OS X itself is failing to retrieve the renewed certificate.
Any suggestions about how to refresh the SSL certificate and force the app to see the new one?