I started developing using sendgrid to make write some email forwarding code. After about 12 hours, I was banned. I emailed them asking why, and here was their response:
"Thank you for contacting SendGrid Support! I would be happy to help you!
I am sorry to hear that you are having troubles logging into your account, I know that is very frustrating.
SendGrid leverages many different vetting techniques and as such we've determined that you're not a good fit for our platform. Because of this, we will not be able to activate your account. Our system does not provide myself or other members of Support with details regarding decisions made in the sign-up process. As such we are not able to provide any more information to you.
I sincerely apologize for this inconvenience.
So basically, sendgrid banned me immediately for reasons they weren't willing to tell me and gave no followup actions. They didn't budge on mentioning any of the reasons why they wouldn't let me have an account, or any followup steps. Sendgrid sucks. Do not use them.