Sendgrid take no responsibility when it comes to their users abusing their service. I constantly have emails blocked because of abuse by another user of SendGrid - and while they assure me that they're doing "all they can", the emails still remain blocked - and I guess sending the emails from another IP address is out of the question...
I have clients complaining that their emails aren't getting sent - and to be able to find out, I need to pay for an addon to my paid account to be able to see the event history via API.
The support person also suggested that I upgrade to a plan, so I'm paying 6 times as much to be able to just have better email deliverability - which is why I started using SendGrid in the flipping first place!
What a crock...