Twilio SendGrid is an email delivery service made by Twilio Inc. Its main product is the SendGrid Email API, through which a business's software creates, sends and manages email at scale; a second product, Marketing Campaigns, gives marketers tools to create email campaigns. SendGrid's website has moved into Twilio.com, with the same products and documentation.
A program sends each message through a RESTful API (a web interface called with HTTP requests) or through SMTP relay, the standard protocol that mail servers use to pass email on. SendGrid then delivers the messages, with domain authentication (SPF and DKIM records that prove the sender may use the domain), dedicated IP addresses on larger plans, suppression management for addresses that should not receive mail, and an email address validation API. Dynamic templates fill in data for each recipient, and an event webhook reports delivery and engagement events back to the sender's systems. Twilio says the platform delivers more than 200 billion emails a month.
SendGrid is a hosted service. A free trial lasts 60 days; after that, plans are monthly subscriptions priced by email volume and features.