hi @RobinPerido
@Osiris is right as to the root cause of the emails
When you run commands such as renew or expand you are not altering the initial certificate. You are in fact creating a new certificate.
Each certificate has a serial number and you can verify that. Certbot and other Clients do a good job of replacing the certificates and updating the symlinks however technically you still have 2 or more certificate issued for that domain. This catches a lot of people out.
The other one that people get caught out on is that the certificates are issued but the installer doesn't work so they issue 5 valid certificates on the same day.
Review the end of this discussion for a bit more of an explanation
Andrei