Minimum recommended SendGrid subscription type

If you are planning to use SendGrid for sending newsletters or mass emails, go with "Pro" (starting at $90./month). The Pro level provides you with a dedicated IP address ascribed to your traffic.

Don't bother with "Essentials", you will be assigned a shared pool of IP addresses, and will be blocked because of questionable activity by previous users of same IPs.

BTW SendGrid Tech. Support are excellent.

(I am a customer, I'm not profiting from this).

We had the same experience.