If a specific port has a certificate problem, it would suggest that the program on that port (in this case Dovecot) isn’t properly set up to deliver the certificate. Maybe your Dovecot needs to be restarted? I can’t really help further than that because you used certbot directly and I don’t know whether those certs have to be moved into another location or anything to make them work.
One thing I noticed is that your box.canadaesports.ca is a CNAME. I think it should be an A entry instead.