mail.oznet.cl is serving a self-signed certificate, not one from Let’s Encrypt. My best guess would be that there’s a second vhost in your configuration with different SSL* directives. Try grep -r "SSLCertificateFile" /etc/httpd/ to find that file.
Using grep -r "SSLCertificateFile" /etc/httpd/, look for values that don't point to a certificate in /etc/letsencrypt. That will in all likelihood be the self-signed certificate apache decided to use for the mail subdomain.
This is assuming the files in /etc/letsencrypt were not somehow manually replaced by a self-signed certificate. You can quickly verify this using openssl x509 -in /etc/letsencrypt/live/mail.oznet.cl/cert.pem -noout -text | grep Issuer:
The output should be "Issuer: C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3".
I found the solution, my virtual host says: ServerAlias mail.oznet.cl but is Servername mail.oznet.cl. Its a Apache bug, works all virtual host but not execute the ssl path when the name of virtualhost is not correctely setting, it is a part of error tolerance of apache.