Gmail locks account when sending mail via Laravel
Since I posted this question, I found a way to solve this issue.
I activated 2-steps authentication for my Google account. Then I generated an application-specific password for my Gmail account and I put this password into my Laravel application.
Now Laravel can send e-mails through my Gmail account :)
Seems like your gmail is preventing the app that is trying to send a mail.
You've to enable the access to the laravel app.
Google's less secure enable
https://www.google.com/settings/security/lesssecureapps
goto that above link and choose enable and then try again. It'll work.