Resend — Sending Email That Actually Arrives
Why you can't just email people from your app directly
Email providers (Gmail, Outlook) aggressively filter mail that looks automated to fight spam. Sending emails reliably at scale requires a dedicated transactional email service that has already built trust with inboxes — Resend is one of these, built specifically for developers.
"Transactional" vs marketing email
"Transactional" emails are triggered by a specific user action — a welcome email on signup, a password reset, a notification. This is different from bulk marketing newsletters, which typically use separate tools optimized for large campaigns rather than instant, one-to-one delivery.
Where 404Fault uses it (and the safety net when it's not configured)
404Fault sends welcome emails, follow/like/comment notifications, and account emails through Resend. If the API key isn't configured yet, the platform queues every email into a Firestore email_outbox collection instead of losing it — a pattern worth remembering: never let a missing external service silently drop data.
Key Takeaways
- Reliable email delivery requires a dedicated service like Resend — raw sending gets filtered as spam.
- "Transactional" emails are triggered by specific user actions, unlike bulk marketing campaigns.
- 404Fault uses Resend for welcome, notification, and account emails.
- A queue (email_outbox) prevents lost emails when the email service isn't yet configured — a good general safety pattern.
Spot transactional vs marketing email
Check your own inbox and find one transactional email (a receipt, a password reset) and one marketing email (a newsletter). Note what's different about their tone and urgency.