They are used by legit businesses and they do a lot in containing spam, so yeah he was wrong.

I don't know or care about spam, but SendGrid is one of the most prolific sources of malware and phishing emails out there. Their opaquely rewritten URLs are an annoyance to security teams everywhere, enough that I've seen enterprises simply block ct.sendgrid.net or any URL with /ls/click, which isn't the kind of thing large companies typically have the will to do.

I work with phishing emails, I love sendgrid, your sandbox sucks if you are not detonating URLs to see where they lead to and rewriting means as soon as sendgrid finds out about an account sending spam/phishing they can disable all those links which isn't doable when they are doing the same thing with multiple domains, urls, subject lines, attachment names,etc... leaving you with live phishing links you don't know about in someone's inbox.

Any modern paid email protection service will also work nicely with sendgrid and the like.

You worked at orgs that didn't have the best decision making if they are blocking sendgrid. Talk about throwing the baby with the bathwater. Lazy mitigations made bad security. This is especially true here since sendgrid is hardly the only one of their kind so you will play whackamole blocking all kinds of legit services because... you don't have toolimg that can follow 301's??

What does your phishing email filtering pipeline look like?

As a bit of anecdata, I received a spam message from SendGrid about 3 weeks ago (while just a few spam messages per year make it through), and that's how I've learned about them. But I guess they won't stay out of DNSBLs for long if the portion of spam messages will be particularly high.

Sendgrid seems to be used as the infrastructure to send emails from a lot of the email service providers I use. They are not spam companies and react to customers who get marked as spam by suspending accounts and doing reviews.

I'm going to guess Sendgrid themselves also look for high ratios of spam reports and do the same.

It is the default service used to manage and send transactional emails out of most Magento instances. It’s basically used like new relic for eCommerce comms. And extra layer of logs/detail/visibility on top of mail logs and a, “baby’s first” EMS/CDP