OpenSMTPD Mail won't send from client, reason=ca-failure

Question

Any time I attempt to send mail from my mail client (In this case, thunderbird), it comes up with an arbitrary error for why it couldn't send the email (The error doesn't matter, as it simply is telling me that the connection got dropped). When I run tail -f /var/log/maillog I see: smtp disconnected reason=ca-failure I can't seem to find anywhere online talking about this and how to fix it.

I've attempted to use several different matching keys and certificates, locally sourced (openssl) and from letsencrypt. OpenSMTP accepts all of these no problem. I have also went as far as to specify the root CA certificate for letsencrypt with their certificates.

Answer 1

Did you define the mail hostname for the OpenSMTPD server?

This file is supposed to be found in /etc/mail/mailname, and it should match the pkiname thats in the smtpd.conf file "pki 'hostname' cert /etc/letsencrypt/live/www.domain.com/cert.pem"

I spent an hour or two fighting with this.

This is defined in the manual :

pki pkiname cert certfile

Associate certificate file certfile with host pkiname, and use that file to prove the identity of the mail server to clients. pkiname is the server's name, derived from the default hostname or set using either /etc/mail/mailname or using the hostname directive. If a fallback certificate or SNI is wanted, the '*' wildcard may be used as pkiname.

A certificate chain may be created by appending one or many certificates, including a Certificate Authority certificate, to certfile. The creation of certificates is documented in starttls(8).