Gmail is also becoming more and more advanced day by day and this feature of auto-reply is one such advancement added to the website, in order to enable an auto-reply option on your Gmail click settings, click on labs tab , click the option enable for canned responses , click save changes for any more information or guidance talk to the http://gmailhelplinenumbercouk.blogspot.com/2018/08/how-to-fix-gmail-authentication-error.html