SENDGRID DELIVER E-MAILS TO 50,000 SUBSCRIBERS *AFTER* THE PROMOTION ENDED. Not one, not twice, but EVERY SINGLE TIME. We got HUNDREDS of customers complaining they received the mail AFTER the promotion campaign ended so they couldn't use the coupon code. Sendgrid refuses to refund and doesn't care about their customers.
SENDGRID IP ARE ALREADY BLACKLISTED. Vast majority of e-mails ends up in the spam folder because SendGrid IP are flagged as spammer (their fault not mine). Because SendGrid IPs are already blacklisted it defeats the purpose of using SendGrid instead of your own mail server. Here's a screenshot of SendGrid customer support explaining their IP are blacklisted: http://prntscr.com/vvftmx
NO REFUND - SENDGRID DOESN'T CARE. They will NOT refund your money even if their service failed due to their own incompetence. They even charged us excess feed of $60 and we never got refunded. Takes many days to get a reply from customer support.
SENDGRID KEEP STEALING YOUR MONEY AFTER CANCELLING YOUR ACCOUNT. We finally had enough of SendGrid's unreliable service and closed our account. But SendGrid kept charging our credit card during 2 months. We had to contact them again twice to get the refund for the money they stole from us.
SendGrid is the only one to blame here. We don't send spam, our domain has very good reputation, we send only 4 e-mails per year, SPF/DKIM/DMARC is correctly configured, etc. The only mistake we did was trusting SendGrid. Don't do the same mistake we did.
I strongly recommend to NOT use SendGrid if you care about your customers. There is not a single valid reason to use SendGrid because their IPs are blacklisted and their service is unreliable. Trust me it will be a disaster for your business if you go with SendGrid, you will learn it the hard way. There are tons of reviews like mine all over the web.