Letsencrypt certificate expires in Thunderbird / Firefox

Hi,
some days ago I renewed all my certificates successfully.
But now I see in Thunderbird and Firefox that the certificate expires on 2017-10-16 (4 days ago).

I got information of my certificate typing the command:
/root/letsencrypt/letsencrypt-auto certificates on my server.

Certificate Name: t2792.greatnet.de
Domains: t2792.greatnet.de www.t2792.greatnet.de
Expiry Date: 2018-01-16 16:01:50+00:00 (VALID: 85 days)
Certificate Path: /etc/letsencrypt/live/t2792.greatnet.de/fullchain.pem
Private Key Path: /etc/letsencrypt/live/t2792.greatnet.de/privkey.pem

That tells me, that the certificate should expire on 2018-01-16

Thank you in advance for help.

Did you use certonly mode with the --webroot or --standalone plugins when you first obtained the certificate, or did you choose automatic installation with one of the --apache or --nginx plugins?

Have you tried reloading your web server?

I used a command like this one:
cd /root/letsencrypt
./letsencrypt-auto certonly -a webroot --webroot-path /srv/www/htdocs -d example.com -d www.example.com

Maybe I did not describe my problem exactly:
My server delivers sites over SSL (https://) - that is working without problems.

But on the client side in Thunderbird, in the menuitem preferences/advanced/certificates/properties I see, that the certificate from my server (running dovecot imap server) has expired.

Of course, I checked the path to the certificate in the Dovecot configuration.

Did you restart dovecot?

sudo systemctl restart dovecot

(Apparently a reload is not sufficient.)

Yes I started dovcot in some ways:
rcdovecot restart it is a Suse server
dovecot
systemctl restart dovecot

I think my question is based on a misunderstanding.

I deleted all that old entries in preferences/advanced/certificates.
These are apparently expired certificates and added exceptions.

After deleting these exceptions, of course I got problems, but problems came from Apparmor on the server. I had to change some paths after having renewed the certificates.
Now I applied the concerning Apparmor profiles and everything is working again.

Firefox and especially Thunderbird now are able to connnect to the server.