You must connect directly to smtp.gmail.com on port 587. Google will no longer accept relayed mail (mail sent through a 3rd-party SMTP server), unless you do a bunch of things like : enable less secure apps in your Google account, use two-factor authentication, use app-specific passwords, answer CAPTCHA questions when you login.
Postman was created to avoid all that trouble but you have to use it in OAuth 2.0 mode. And that doesn’t work over port 587. Did you use Postman’s Setup Wizard?
Hola ekkamag. Hablas Inglés? Mi Español no muy bien 😉 Quiero ayudarle con su problema. ¿Cuál es el error llegaste con Postman SMTP? Se puede tratar la función «Run a Port Connection Test»?
¿Tiene Gmail?
