sabarish
It looks like Gmail isn't allowing you to relay for some reason. In this case it appears you will need to set SMTP server port to 587, set Connection security to either STARTTLS or SSL/TLS, set Authentication to Username and password, input your email's username and password, and retest. This is not an osTicket issue so I'd highly recommend reaching out to Hosting/Zabbix provider for further assistance.
Cheers.