If you believe your account has been compromised, please log in to your account and change your account username and password immediately under the SendGrid Account Settings page. You will also need to update the username and password in your sending application or code in order to get mail flowing again.
After changing your account username and password, please contact support. We can help you investigate, and get our Compliance team involved if necessary.
We'll try and help you isolate any issues or vulnerabilities with your SendGrid integration. We can also temporarily deactivate your account as well as delete any messages that are currently in a pending state within our system. In some cases your account may have already been preemptively Suspended to prevent damage to your reputation, in these cases please check your email for a notification from our Compliance department and respond directly to it to get the ball rolling.