That would be because sendgrid is lame.

I've recently tried to use their service to send emails, club member newsletters. I've never thought much about bulk e-mails before and I thought it was a "solved problem" by now. Sendgrid are well known so they were my first choice.

During initial testing I found both bugs in the API and missing functionality. I've worked over 20 years with IT and yet sendgrid support is easily on the top-3 list of my worst support experiences, a total waste of time.

We ended up using mailgun instead and so far it looks much better.