Gmail error: Please log in via your web browser and then try again

Situation

My web application sends email messages from website with gmail-account smtp credentials (login / password / SMTP server / port)

Error

When debugging an application on the local server - everything is OK.
Once the load on Web Hosting - i've got an error

534-5.7.14 Please log in via your web browser and then try again. 534-5.7.14 Learn more at 534 5.7.14 https://support.google.com/mail/bin/answer.py?answer=78754 18sm42904851wju.15 - gsmtp

Research

Googling helps. Оne of the answers here was usefull
http://stackoverflow.com/questions/20337040/gmail-smtp-debug-error-please-log-in-via-your-web-browser

Solution

The essence of the problem in my case:
Gmail blocks mails from unknown IP-addresses.
I wasn't able do the Google's advice ("Please log in via your web browser") from IP addres of my hosting server.

So, it was necessary to turn off the google blocking of unknown address through this link
https://accounts.google.com/DisplayUnlockCaptcha

UPD
Also I allow unsecured Apps on the page
https://myaccount.google.com/lesssecureapps

Related links

Gmail SMTP debug: error “please log in via your web browser”
http://stackoverflow.com/questions/20337040/gmail-smtp-debug-error-please-log-in-via-your-web-browser