Step 1:
Using letsencrypt we are going to download the SSL for Domain sitinwhm-ispconfig.sageit.in
For that we are going to downloads Wildcard SSL.
Step 2:
Upload the certificate, key & cabundle file in server in folder /home/ispconfig
Step 3:
Take the backup of file in Local
/etc/postfix/smtpd.crt
/etc/postfix/smtpd.key.
/etc/postfix/cabundle.crt
/etc/dovecot/dovecot.conf
Step 4:
rename the smtpd.crt, smtpd.key & cabundle.crt to oldsmtpd.crt, oldsmtpd.key & oldcabundle.crt
Rename the downloaded certificate to smtpd.crt, smtpd.key & cabundle.crt
Step 5:
Upload the downloaded certificate to location /etc/postfix
Step 6:
Restart the postfix and dovecot server
service postfix restart
service dovecot restart
Step 7:
verify the certificate is updated or not.