Install custom sertificate

Hello there, I installed SSL certificate to my email server but it was an error.
I have 3 domains and it subs. The following structure might help describing this.
Domain : mydomain.com
Sub 1 : www.mydomain.com
Sub 2 : mail.mydomain.com

The domain and the Sub 1 have correctly installed SSL Certificate from StarSSL but the Sub 2, mail.mydomain.com was not correctly gain the certificate.

The problem is mydomain.com and _www.mydomain.com certificates are gained by submitting the provided CSR on the admin page while mail.mydomain.com gaining certificate by generating self-signed CSR.

I installed the certificate for mail.mydomain.com into the path directive /home/user-data/ssl/www.mail.mydomain.com/ssl_certificate.pem and the key file into /home/user-data/ssl/www.mail.mydomain.com.

And then nginx settings in /etc/nginx/conf.d/local.conf also changed by me in the certificate path. from /home/user-data/ssl/ to /home/user-data/ssl/www.mail.mydomain.com

The access of the site in address _https://mail.mydomain.com/admin is done without a problem. but after I restart my system the file /etc/nginx/conf.d/local.conf is automatically reset. Please help me keep this settings to be always exist…!indent preformatted text by 4 spaces

I’m not an expert, but I personally would either get a wildcard ssl (*.domain.com), or a completely separate ssl for mail.mydomain.com.

Thanks for reply. If no way to keep that setting on, your advice will be a good choice.