SendGrid retired its free plan — new accounts get a short trial, then a card. Developers who just need an app to send password resets and receipts have moved on; these SendGrid alternatives still run real free tiers.
Send marketing campaigns and transactional mails
Resend: 3,000 emails a month free, an API developers actually enjoy, two-minute setup. Brevo if you want email plus a marketing suite under one free tier.