some of my clients set Let's Encrypt Certificate, and after some time his domain expire. Let's Encrypt can't renew cert for that domain and I get message about it EVERY DAY, how can I disable messages about it?
The message you get should not be your concern. The certificate will be attempted to be renewed every night for the rest of your server life until you disable renewal for the domain or delete the domain. If you could disable the email notice, that would not help you and would not solve any problem. You should take care of managing your server, that mean you should disable renewal for the domain, so that it is not attempted to be renewed every night for the rest of your server life.