Postmark vs Knock
Reliable transactional email with fast delivery
vs. Notifications-as-a-service: in-app feeds, email, push, SMS, chat via one API
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
Knock
Developer
Free forever. 10K messages, 500 guide users, 500 AI credits/month.
$0 base (usage-based)
Starter
$250/mo. 50K messages, 2.5K guide users, 2K AI credits. Remove branding.
$250/mo
Enterprise
Custom pricing. White-label, i18n, data warehouse, Datadog, SCIM, SAML, HIPAA/BAA.
Custom
Free-tier quotas head-to-head
Comparing free on Postmark vs starter on Knock.
| Metric | Postmark | Knock |
|---|---|---|
| guide users | — | 2500 users |
| guide users overage | — | $0.05/user USD/user |
| messages monthly | — | 50000 messages/mo |
| messages overage | — | $0.005/message USD/message |
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.
Knock · 13 features
- AI Agents — Autonomous notification drafting & workflow generation.
- Batch + Digest — Group notifications into digests on schedule or window.
- Chat — Slack, Microsoft Teams, Discord.
- Email — Send via SendGrid/Postmark/Resend/Mailgun/AWS SES as relays.
- Guides — In-product messaging, announcements, modals, banners.
- i18n / Localization — Translate templates by user locale.
- In-App Feed — Notification inbox with React/Vue/iOS/Android drop-in components.
- Multi-tenancy — Per-tenant branding, preferences, quiet hours.
- Outbound Webhooks — Subscribe to delivery events.
- Preferences — User + tenant preference center with granular controls.
- Push — iOS (APNs), Android (FCM), Expo, Web Push.
- SMS — Twilio, MessageBird, Telnyx, Vonage as providers.
- Workflows — Visual notification orchestration (branch, batch, delay, throttle).
Developer interfaces
| Kind | Postmark | Knock |
|---|---|---|
| CLI | — | Knock CLI |
| SDK | postmark-dotnet, postmarker (Python), postmark-go, postmark (Node), postmark-php, postmark-rails | knockapi (Python), knockapi (Ruby), knock-elixir, knock-go, knock-java, @knocklabs/node, @knocklabs/react |
| REST | Postmark REST API | Knock REST API |
| MCP | — | Knock MCP Server |
| OTHER | Inbound Email, SMTP Relay, Webhooks | Outbound Webhooks |
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