Expired certificates issue

[hede]

Am 07.01.2020 12:32, schrieb Hernan Saltiel:
> I do not have the certbot directory, what I have is a self signed
> certificate, that expired. The Outlook window do not state that the
> certificate is invalid because it's self signed, but because has
> expired.

There's plenty of help out there how to renew self signed certificates, 
like this one for red hat based distributions (my first search hit for 
red hat based distributions):
https://www.stevejenkins.com/blog/2010/08/renewing-a-self-signed-ssl-certificate-on-fedoracentos/

(The default self-signed cert for debian is valid many years, so you're 
probably using a red hat based distribution!?  - correct me if I'm 
wrong.)

There's no kolab specialty in it, you can use any method your OS 
supports. You probably have to adapt path-names to your key and cert (if 
they are different), like is said within the how to. The give an example 
for Apache, this one is for postfix:

grep -e "tls_cert_file" /etc/postfix/main.cf

... it should show you where postfix will expect your cert/key to 
reside.

> All this was previously configured, when initially installed the
> server, with the certs I created.

Presumably it's the OS default key/cert - created by the installer for 
testing purposes. It should be possible to renew it the way designated 
by your OS designer. Or better: replaced by some valid CA certificate.

Btw: Why self signed at all? I wonder if Outlook accepts the self signed 
cert without a warning? I - for myself - would prefer to use some valid 
CA certificate, currently royalty free Let's Encrypt certificates.

Nevertheless it's absolutely fine to use self singed certificates. 
Rolling out a self made CA or Checking fingerprints by hand is actually 
_more_ secure than the currently used internet-wide CA system.

regards
hede