Postmark vs OneSignal
Reliable transactional email with fast delivery
vs. Mobile + web push, email, SMS, and in-app messaging at consumer scale
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
OneSignal
Free
Unlimited mobile push, 10K web push subs, 10K email/mo, 1 journey. GDPR compliant.
Free
Growth
$19/mo + usage. 20K email/mo included, then $1.50/1K. 3 journeys. Advanced in-app.
$19/mo
Professional
Custom. Unlimited volume, 20 journeys, CSV export, prioritized support.
Custom
Enterprise
Custom. Dedicated CSM, SLA, frequency capping, advanced permissions, HIPAA options.
Custom
Free-tier quotas head-to-head
Comparing free on Postmark vs free on OneSignal.
| Metric | Postmark | OneSignal |
|---|---|---|
| active journeys | — | 1 journeys |
| email monthly | — | 10000 emails/mo |
| mobile push | — | Unlimited subscribers |
| web push subscribers | — | 10000 subscribers |
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.
OneSignal · 12 features
- A/B Testing — Split testing across push, email, in-app.
- Analytics + Cohorts — Delivery, open, click, conversion metrics + retention cohorts.
- Email — Transactional + marketing email with templates.
- Frequency Capping — Limit message frequency per user.
- In-App Messaging — In-app banners, modals, surveys, carousels triggered by events.
- Intelligent Delivery — Optimize send time per user with ML.
- Journeys — Multi-step automations with branching, delays, actions.
- Live Activities — iOS Dynamic Island + Live Activities.
- Mobile Push — iOS (APNs), Android (FCM/HMS) push notifications.
- Segments — Dynamic audience targeting by tags, location, behavior.
- SMS — Two-way SMS in 200+ countries.
- Web Push — Browser push via service workers (Chrome, Firefox, Edge, Safari, Opera).
Developer interfaces
| Kind | Postmark | OneSignal |
|---|---|---|
| SDK | postmark-dotnet, postmarker (Python), postmark-go, postmark (Node), postmark-php, postmark-rails | OneSignal Android SDK, onesignal_flutter, OneSignal iOS SDK, @onesignal/node-onesignal, OneSignal Unity SDK, OneSignal Web SDK, react-native-onesignal |
| REST | Postmark REST API | OneSignal REST API |
| OTHER | Inbound Email, SMTP Relay, Webhooks | Outbound Webhooks |
Staxly is an independent catalog of developer platforms. Some links to Postmark and OneSignal may be affiliate links — Staxly may earn a commission if you sign up through them, at no extra cost to you. Pricing is verified against vendor pages at publication time — reconfirm before buying.
Want this comparison in your AI agent's context? Install the free Staxly MCP server.