2
Okay, turns out it had nothing to do with my code. Gmail was not happy with my account being accessed from Ashburn, VA, EUA (where Heroku supposedly does it’s thing). So I had to play a little bit with my configurations and in the end I changed the password for a new (more secure) one and everything started to work just fine.
In short:
THE ISSUE WAS WITH GMAIL
CHANGED THE PASSWORD AND IT STARTED TO WORK
Source:stackexchange.com