Twilio SendGrid: long-standing email API + marketing campaigns. Free 100/day tier; widely documented in every language.
SendGrid
The incumbent email API with marketing tools bolted on
sendgrid.com · Free 100/day; from $19.95/mo
Capabilities
Best for
- Teams already on Twilio; legacy-documented integrations
Not for
- New builds (Resend/Postmark have better DX and deliverability stories)