How to solve Google SMTP Server attempt prevent error ?

Before some time, I am working on my ASP.NET Project and Send mail to customer Email Address using Google Gmail SMTP Service Provide, but Google say me "Sign-in attempt prevented" and apear bellow message in my Gmail inbox:

Hi Unique

Someone just tried to sign in to your Google Account ........ from an app that does't meet modern security standards....

And after see message, Just i enable "Less secure apps" and SMTP working Fine and problem solve..

Gmail SMTP Configuration
smtp.Host : smtp.gmail.com
smtp.Port  : 587
smtp Username: your Gmail ID
smtp Password : your Gmail Password
More visit: Google Apps SMTP Setting Official

Less Secure Apps Access URL: 
https://www.google.com/settings/security/lesssecureapps