cyrus-imap re-creating the TLS/SSL Certificate when certificate expired

openssl req -new -nodes -out req.pem -keyout key.pem 
openssl rsa -in key.pem -out new.key.pem
openssl x509 -in req.pem -out ca-cert -req  -signkey new.key.pem -days 999
mkdir /var/imap
cp new.key.pem  /etc/pki/cyrus-imapd/server.pem
rm new.key.pem 
cat ca-cert >> /etc/pki/cyrus-imapd/server.pem
grep cyrus /etc/passwd
grep cyrus /etc/group
chown cyrus:saslauth /etc/pki/cyrus-imapd/server.pem
chmod 600 /etc/pki/cyrus-imapd/server.pem

vi /etc/imapd.conf
#tls_cert_file: /etc/pki/cyrus-imapd/cyrus-imapd.pem
#tls_key_file: /etc/pki/cyrus-imapd/cyrus-imapd.pem
#tls_ca_file: /etc/pki/tls/certs/ca-bundle.crt
tls_ca_file: /etc/pki/cyrus-imapd/server.pem
tls_cert_file: /etc/pki/cyrus-imapd/server.pem
tls_key_file: /etc/pki/cyrus-imapd/server.pem

In email client side:
Security setting
Security connect: STARTTLS Port: 110
Security auth: Normall password