SGD is going to look into why Postfix is not loading the new certificates as soon as he can, but in the meantime, if this happens again, log into mail.earthclick.net.

As root,

cd /etc/postfix/virtdomains

postmap -F lmdb:sni

postfix reload

That will rebuild the SNI database with the current certificate for all domains, and reload Postfix so it will use the updated database.

Again, this isn't a certificate renewal issue - it's a Postfix not loading the new certificate issue.