Ask HN: Is SendGrid causing difficulty for anyone else on Subuser accounts?

We have around 80 subusers on Sendgrid and have used them for over 4 years. These subusers are all legitimate businesses with great reputations. SendGrid has now been randomly suspending them and will not let us add any more accounts. Our account was originally created through Heroku. I have loved their service...but the last few weeks has me second guessing our decision to use them. Anyone else have suggestions for alternatives or better ways to talk to SendGrid?