Apache not running

When I changed the hostname of my server the apache stopped working.

Now the log is showing following messages

The part of log:

Redirecting to /bin/systemctl restart  httpd.service
Job for httpd.service failed because the control process exited with error code. See "systemctl status httpd.service" and "journalctl -xe" for details.

Oct 26 06:47:08 mailer.boxygen.ml postfix/smtpd[14485]: warning: cannot get RSA certificate from file /etc/pki/tls/certs/mailer.boxygen.ml.crt: disabling TLS s
Oct 26 06:47:08 mailer.boxygen.ml postfix/smtpd[14485]: warning: TLS library problem: 14485:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:70
Oct 26 06:47:08 mailer.boxygen.ml postfix/smtpd[14485]: warning: TLS library problem: 14485:error:140DC009:SSL routines:SSL_CTX_use_certificate_chain_file:PEM
Oct 26 06:47:08 mailer.boxygen.ml postfix/smtpd[14485]: warning: hostname 161-22-62-2.petrynet.com.br does not resolve to address 161.22.62.2: Name or service


I don't have any SSL Certificate installed but it is giving error due to that.

How to resolve this.

Have you recently made any changes?

try deleting certificate files mentioned in the error message and then try again to save the hostname.
/etc/pki/tls/certs/mailer.boxygen.ml.cr