When I used Amazon SES, I had to put TXT records in my DNS so that Yahoo/Gmail knows that the server is allowed to send from my domain name.
However, when I signed up for Heroku and Sendgrid Add-on (Free edition), I was not required to enter any TXT fields. Why?
How does Gmail know that Sendgrid is "authorized" to send on behalf of my domain name if I do not enter records in DNS?
As of right now, I could send
From: email@example.com using Sendgrid??