Sending model
SendMailOS
Use hosted delivery or connect a sending server that you operate. The application remains managed by SendMailOS.
Postmark
Postmark provides managed API/SMTP sending with Transactional and Broadcast Message Streams.
Compare email platforms
SendMailOS vs Postmark: campaigns and application email
Compare SendMailOS and Postmark for API and SMTP email, marketing workflows, message streams and the cost of running your own sending server.
SendMailOS and Postmark, side by side
Marketing workflow
SendMailOS
Use subscriber audiences, editable templates and visual automations in the dashboard.
Postmark
Broadcast Streams carry one-to-many email such as newsletters. Confirm how you will build audiences and author campaigns in your chosen setup.
Integration checks
SendMailOS
Test your API requests, SMTP client, signed webhooks, suppression and reply capture before switching.
Postmark
The original Transactional stream is the default; explicitly select a different stream for the intended traffic.
Cost basis
SendMailOS
Subscription, hosted allowance and your VPS cost are separate. Own-server emails do not consume hosted credits.
Postmark
Pricing is based on monthly sent/received email and feature tier. Inbound processing is included with Pro and Platform.
Checked 24 October 2026 using the official sources below. This is a SendMailOS comparison, not an independent performance test.
Compare the complete sending cost
Unlimited emails with your own server, from €12/month
Starter includes 10,000 active subscribers, one connected server and 25,000 hosted emails per billing month. Emails actually sent through your connected server have no monthly platform email quota and do not use hosted credits.
Your VPS is billed separately. Warm-up, fair use, server capacity, subscriber limits and other plan limits apply. A connected server does not guarantee inbox placement.
See how own-server sending worksPostmark: the published cost model
At the published 10,000-email tier, Postmark lists Basic at US$15/month, Pro at US$16.50 and Platform at US$18. Basic lists extra email at US$1.80 per 1,000; higher tiers differ. Check the selected tier and total volume before budgeting.
SendMailOS prices are in EUR. Competitor USD examples are labelled US$ and are not converted. Billing terms, taxes, selected features and usage can change the final invoice. Entry examples are not equal-capacity quotes.
Match the same audience and sending pattern
For 10,000 active subscribers receiving ten newsletters in a month, budget for 100,000 recipient sends, plus application email and any receiving usage. Compare the appropriate Postmark volume tier with your SendMailOS route and plan; the published Postmark 10,000-email entry is not a quote for that scenario.
A transparent SendMailOS example
10,000 active subscribers, 100,000 own-server recipient sends per month and one suitable server: Starter €12 + an illustrative €8 monthly VPS estimate = €20/month. This assumes the server can handle that volume under warm-up and sending safeguards. It is not a VPS quote, a capacity promise or a hosted-send quote. The separate Starter hosted allowance remains 25,000 emails.
Which model fits your team?
Consider SendMailOS
Consider SendMailOS when your team wants campaign creation, audiences, visual follow-ups and reply conversations alongside API/SMTP, with a choice of hosted or own-server delivery.
Evaluate Postmark
Evaluate Postmark when its message-stream model and developer integration fit the emails you send. Keep a working integration until the replacement passes your own acceptance checks.
Test before switching
Record the current behavior
List required integrations, audience fields, message types, exclusions, schedules and reports. Preserve consent records and suppression states separately from active subscribers.
Rebuild a representative example
Separate transactional messages from marketing messages in the test plan. Check the chosen stream or route, recipient suppression, unsubscribe behavior, event meanings, retries and reply handling. Keep a copy of the event payloads you depend on.
Compare observed outcomes
Check the received message, delivery events, links, personalization, unsubscribe and any reply path using mailboxes you control. A recorded open is not proof that a person read the email; an accepted message is not an inbox-placement guarantee.
Move only after the test passes
Verify your domain and selected route, reconcile audience counts and pause the previous workflow before enabling its replacement. Plan a gradual sending transition and retain the source export for recovery.
Choose the plan that fits your limits
Starter · €12/month
25,000 hosted emails per billing month.
10,000 active subscribers.
1 connected sending server.
Growth · €39/month
100,000 hosted emails per billing month.
50,000 active subscribers.
3 connected sending servers.
Pro · €99/month
250,000 hosted emails per billing month.
250,000 active subscribers.
10 connected sending servers.
Every paid plan includes own-server access. More than 10,000 active subscribers or more than one connected server does not fit Starter. Domain, team, automation, API and other limits also apply.
Check every plan limitQuestions before you choose
Does Postmark support newsletters?
Yes. Postmark Broadcast Message Streams are designed for one-to-many email, including newsletters and product announcements. Compare the surrounding audience and campaign workflow you need.
Are unlimited daily sends the same as unlimited monthly email?
No. A daily-limit policy does not remove the monthly email allowance or overage charges. In SendMailOS, the unlimited own-server offer applies to messages actually delivered through your connected server; hosted allowances remain separate.
Will my current API calls work unchanged?
Do not assume API compatibility. Map authentication, request fields, response statuses, webhooks and retry behavior, then test your integration before moving production traffic.
Official sources and comparison notes
Reviewed by SendMailOS on 24 October 2026. Product documentation supports the scoped facts above; live behavior and suitability still need testing with your setup. Recheck current prices and limits before purchase.
- Postmark pricing and feature tiers
- Postmark Transactional and Broadcast Message Streams
- SendMailOS plans and limits
- SendMailOS own-server route and VPS requirements
Competitor names identify the compared products. No affiliation or endorsement is implied.
Keep comparing
Test your next email workflow
Start with 3,000 free hosted emails per billing month and up to 2,000 active subscribers. Own-server delivery starts on Starter from €12/month, with VPS costs and plan limits.