trevelyan, I work at SendGrid in Support. Our Support engineers are on (chat) 24/7. Sorry about the suspension. Sometimes when we detect behavior that may damage your sending reputation we put the brakes on so that we can make sure things are going as planned and/or offer advice. All email systems attract spammers. These filters allow us to continually send email reliably. No system is perfect and sometimes legit sending may look suspicious. We want to partner with you to make sure you're successful. Lifting the suspension can be done with one call, chat or email. Again, sorry if our actions were mistaken as malicious. Reach out and we'll help. https://support.sendgrid.com/hc/en-us/articles/203979566
Shawn