Postmark vs GrowthBook
Reliable transactional email with fast delivery
vs. Open-source feature flags + experimentation — Warehouse Native
Pricing tiers
Postmark
Free
100 emails/month forever. No credit card. Side projects and testing.
Free
Basic — 10k
10,000 emails/month. Overage $1.80/1k. Unlimited emails/day.
$15/mo
Pro — 10k
10,000 emails/month. Overage $1.30/1k. Inbound email + message streams.
$17/mo
Platform — 10k
10,000 emails/month. Overage $1.20/1k. Team collab, more domains.
$18/mo
Enterprise (>1.5M)
Custom for senders exceeding 1.5M/month.
Custom
GrowthBook
Open Source (Self-Host)
MIT-licensed. Unlimited everything. Community support.
$0 base (usage-based)
Cloud — Starter (Free)
Up to 3 users. Unlimited flags + experiments. Warehouse Native included.
Free
Cloud — Pro
$40/user/month. Up to 50 users. Advanced stats, visual A/B editor, CUPED, sequential testing, bandits.
$40/mo
Cloud — Enterprise
Custom. Unlimited users, SSO/SAML, approval flows, data pipelines, exportable audit logs.
Custom
Self-Host Enterprise
Open Source + Enterprise license. Visual A/B editor, advanced metrics, SSO/SAML, approvals, training.
Custom
Free-tier quotas head-to-head
Comparing free on Postmark vs oss on GrowthBook.
| Metric | Postmark | GrowthBook |
|---|---|---|
| No overlapping quota metrics for these tiers. | ||
Features
Postmark · 12 features
- Activity Search — Full-text search over sent messages for 45-365 days.
- Bounce Handling — Automatic hard/soft bounce detection + suppression management.
- Broadcast Messages — Via separate Broadcast Message Stream. Bulk sends with throttling.
- DKIM + SPF — One-click verification + auto-renewal of DKIM keys.
- Inbound Email — Route inbound emails to your webhook. Parse attachments, threads.
- Message Streams — Isolate transactional from marketing for separate deliverability reputation.
- Open + Click Tracking — Configurable at template or send level.
- Raw API Access — 100+ endpoints for bounces, servers, tags, templates, stats.
- Servers — Multi-tenant isolation: each "server" has its own API token + reputation.
- Templates — Mustachio template language with variables, alias + versioning.
- Transactional Send — Reliable API for password resets, receipts, notifications. Sub-10s delivery.
- Webhook Events — Delivery, bounce, spam complaint, open, click, subscription change.
GrowthBook · 15 features
- Approval Flows — Require reviewer approval on flag changes. Enterprise.
- Audit Logs — Full change history. Exportable on Enterprise.
- Dimensions & Slicing — Break down experiment results by user dimensions.
- Edge SDK Support — Cloudflare Workers, Lambda@Edge, Fastly, Akamai EdgeWorkers, Netlify Edge.
- Experiments — A/B/n with CUPED variance reduction + sequential testing.
- Feature Flags — Boolean + string + number + JSON flags with targeting.
- Feature Reviews (PR-style) — Draft → review → approve flag changes.
- Guardrail Metrics — Auto-monitor key metrics during experiments.
- Metric Catalog — Define + reuse metrics across experiments.
- Multi-Armed Bandits — Adaptive traffic allocation. Pro+.
- Safe Rollouts — Guarded gradual rollouts with automatic rollback.
- SSO / SAML — Enterprise SSO for cloud + self-host EE.
- Sticky Bucketing — User stays in variant even after eligibility changes.
- Visual A/B Test Editor — No-code DOM editor for web experiments. Pro+.
- Warehouse Native — Connect your warehouse + run experiments against your events data.
Developer interfaces
| Kind | Postmark | GrowthBook |
|---|---|---|
| SDK | postmark-dotnet, postmarker (Python), postmark-go, postmark (Node), postmark-php, postmark-rails | Edge SDKs (CF Workers / Lambda@Edge / Fastly / Akamai), growthbook-android, growthbook-flutter, growthbook-go, growthbook-java, growthbook-node, growthbook-php, growthbook-python, growthbook-ruby, growthbook-swift, sdk-javascript, sdk-react |
| REST | Postmark REST API | GrowthBook REST API |
| OTHER | Inbound Email, SMTP Relay, Webhooks | Webhooks |
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