feat: add NeverBounce email verification for transactional emails#1499
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evanjacobson wants to merge 5 commits intomainfrom
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feat: add NeverBounce email verification for transactional emails#1499evanjacobson wants to merge 5 commits intomainfrom
evanjacobson wants to merge 5 commits intomainfrom
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Adds pre-send NeverBounce verification to reduce ~3% bounce rate on transactional emails. Blocks invalid and disposable emails; allows valid, catchall, and unknown through. Fails open if NeverBounce is unavailable. Callers receive SendResult so they can react to blocked emails: - Magic link route returns 400 with user-facing error - Org invite expires invitation row and throws BAD_REQUEST - Billing lifecycle cron removes idempotency row for retry - Admin email testing routes through send() for verification
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Code Review SummaryStatus: No Issues Found | Recommendation: Merge Files Reviewed (2 files)
Reviewed by gpt-5.4-20260305 · 145,455 tokens |
- Admin sendTest restores original provider-specific routing (respects selected provider) with NeverBounce check added before dispatch - send() now checks provider return value — returns provider_not_configured when credentials are missing instead of falsely claiming sent: true - SendResult reason union extended with 'provider_not_configured'
evanjacobson
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Mar 24, 2026
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most of this will be filtered out after #1356 merges
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- Magic link route: neverbounce_rejected → 400 (user's email is bad), provider_not_configured → 500 (server issue, don't blame the user) - Billing cron: only deletes idempotency row for provider_not_configured (transient). Keeps the row for neverbounce_rejected (terminal) to avoid re-verifying the same invalid address every sweep.
evanjacobson
commented
Mar 24, 2026
| execution_time: number; | ||
| }; | ||
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| const BLOCKED_RESULTS = new Set<NeverBounceResult>(['invalid', 'disposable']); |
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note that 'disposable' was not explicitly included in the spec, but is included here. 'disposable' emails are services such as tempmail, guerilla mail, etc.
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Summary
Adds NeverBounce email verification before sending transactional emails to reduce our ~3% bounce rate. Blocks
invalidanddisposableemails; allowsvalid,catchall,unknownthrough. Fails open if NeverBounce is unavailable.How it works:
src/lib/email-neverbounce.tscalls the NeverBounce single-check API with a 5s timeoutsend()returnsSendResult({ sent: true } | { sent: false, reason }) so callers can reactCaller handling:
BAD_REQUESTsend()so NeverBounce is exercisedVerification
Automated tests (50 passing)
npx tsc --noEmit— no type errorspnpm lint— cleanemail-neverbounce.test.ts— 11 tests (all result types, fail-open, Sentry reporting, timeout, params)magic-link/route.test.ts— 10 testsautoTopUp.test.ts— 16 testsemail.test.ts— 13 testsManual tests (all passing on localhost)
fakeperson@xyznotarealdomainever.comtld→ HTTP 400test@mailinator.com→ HTTP 400support@neverbounce.com→ HTTP 200evan@kilocode.ai→ email received in inboxVisual Changes
N/A — no UI changes in this PR (admin page provider selector is unchanged).
Reviewer Notes
NEVERBOUNCE_API_KEYhas been added to Vercel.