On April 6, 2020, SendGrid changed its sender verification requirements for new accounts created since April 6, 2020. If your SendGrid account was created before April 6, 2020, then the following may still apply to you if you were asked to authenticate a domain in order to send emails.

Several users have recently reported that when signing up for Sendgrid, so that they can send unlimited emails with Gmail, Sendgrid is requiring a domain whitelabel setup as part of their verification process. Not doing so limits the Sendgrid account to sending 100 emails/day.