Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. https://crt.sh/?q=example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
My domain is:correo.grupomk.com.ar
I ran this command:/opt/zimbra/bin/zmcertmgr verifycrt comm privkey.pem cert.pem chain.pem
It produced this output:ERROR: Unable to validate certificate chain: cert.pem: C = US, O = Let’s Encrypt, CN = Let’s Encrypt Authority X3
error 2 at 1 depth lookup:unable to get issuer certificate
My web server is (include version):ngnix (zimbra)
The operating system my web server runs on is (include version):ubuntu 16
I can login to a root shell on my machine (yes or no, or I don’t know):yes