Postmark charges by monthly email volume, not by a prepaid credit balance. As of July 2026, it offers four plans: a permanent Free tier (100 emails/month), Basic ($15/mo), Pro ($16.50/mo), and Platform ($18/mo). Basic, Pro, and Platform all include 10,000 emails/month, and every email you send beyond that, whether transactional or broadcast, bills at a per-1,000 overage rate that gets cheaper on the higher tiers. There is no annual discount and no rollover: unused volume resets every billing period.
That per-email overage rate, not the base price, is what actually determines your bill once you’re sending meaningfully more than the included 10,000. This post breaks down each plan, how message streams share (or don’t share) your quota, what dedicated IPs and retention cost extra, and a worked example showing where the cheaper-looking plan stops being cheaper.
Postmark’s Four Plans, Side by Side
All figures below are pulled directly from Postmark’s pricing page as of July 2026.
| Plan | Monthly price | Included volume | Overage rate | Data retention |
|---|---|---|---|---|
| Free | $0 | 100 emails/month | Not available (hard cap) | 45 days |
| Basic | $15.00 | 10,000 emails/month | $1.80 / 1,000 | 45 days |
| Pro | $16.50 | 10,000 emails/month | $1.30 / 1,000 | Up to 365 days (45-day default) |
| Platform | $18.00 | 10,000 emails/month | $1.20 / 1,000 | Up to 365 days (45-day default) |
The Free plan has no expiration date. Postmark’s own pricing page states new accounts “start off on our free developer plan with 100 emails per month” and that “it doesn’t expire,” making it usable indefinitely for staging environments or low-volume side projects rather than a time-limited trial. The tradeoff is that the Free plan does not allow overages at all, so it stops delivering once you hit 100 emails in a billing period.
Base prices across Basic, Pro, and Platform are close (a $3 spread), but the overage rate is where the real difference shows up. Basic costs $1.80 for every extra 1,000 emails, Pro costs $1.30, and Platform costs $1.20. Once you’re regularly sending past the included 10,000, the plan with the lowest base price is not necessarily the cheapest option.
Message Streams: One Quota for Transactional and Broadcast Mail
Postmark separates email traffic into message streams: transactional streams for one-to-one triggered mail (password resets, receipts, notifications) and broadcast streams for one-to-many sends (product updates, newsletters). The two run on genuinely separate infrastructure, including separate IP ranges, so a broadcast send can’t hurt the deliverability of your password-reset emails.
That separation is about infrastructure, not billing. Postmark’s documentation is explicit that both stream types draw from the same monthly allowance: any email you send through Postmark counts toward your plan’s monthly limit, transactional and broadcast alike. There’s no separate broadcast quota to buy and no discount for routing marketing sends through their own stream. Stream limits do scale with plan tier: Basic allows up to 15 streams, Pro up to 30, and Platform is unlimited, which matters more for teams organizing multiple products or environments than for raw volume.
If you’re wiring streams up through the API rather than the dashboard, the mechanics are covered in Postmark’s message streams API documentation, and our guide to the email API for programmatic sending covers the broader integration patterns.
Retention, Dedicated IPs, and What Else Scales With Plan Tier
Two costs are easy to miss when comparing plans on price alone:
- Data retention. Free and Basic cap activity log retention at 45 days. Pro and Platform allow customizable retention up to 365 days, still defaulting to 45 days unless you change it. If you need a year of bounce and open history for compliance or debugging, that’s a Pro-or-higher requirement, independent of send volume.
- Dedicated IPs. A dedicated IP starts at $50/month per IP and is only available on Pro plans or higher. Basic and Free accounts send from Postmark’s shared IP pool. For most transactional senders under a few hundred thousand emails a month, a shared pool with good reputation management outperforms a dedicated IP that isn’t warmed up correctly, but high-volume senders with strict deliverability requirements often want the dedicated option regardless of cost.
Neither retention length nor stream count is billed as a separate line item. They’re bundled into the plan tier itself, which is part of why Pro, at $16.50/mo, is positioned as Postmark’s “Most Popular” option: it’s the cheapest tier that unlocks extended retention and dedicated IP eligibility.
Worked Example: When the Cheaper Plan Stops Being Cheaper
Say a SaaS product sends 45,000 transactional emails a month: password resets, receipts, and in-app notifications combined.
On Basic: $15.00 base + 35,000 overage emails at $1.80/1,000 = $15.00 + $63.00 = $78.00/month.
On Pro: $16.50 base + 35,000 overage emails at $1.30/1,000 = $16.50 + $45.50 = $62.00/month.
Pro comes out $16 cheaper per month at this volume, despite having a higher base price. The crossover point (where Pro’s lower overage rate offsets its $1.50 higher base price) works out to about 3,000 overage emails, or roughly 13,000 emails total in a billing period. Below that volume, Basic is marginally cheaper. Above it, Pro wins, and the gap widens as volume grows. Platform’s $1.20 overage rate pulls further ahead again once you’re sending in the hundreds of thousands per month, though its main draw for most teams is the unlimited stream count rather than the overage discount alone.
The practical takeaway: don’t pick a Postmark plan by base price. Estimate your actual monthly send volume, including both transactional and broadcast traffic since they share the same quota, and run the math on total cost at that volume before committing.
Why Postmark Costs More Per Email Than Bulk-Volume Senders
Postmark’s per-email price is higher than what you’ll find from providers built around large marketing sends, and that’s a deliberate positioning choice rather than an oversight. Postmark states directly that “delivery shouldn’t be an add-on or up-charge,” building deliverability infrastructure into every plan rather than selling it as a premium tier. The company also describes its message-stream separation as ensuring transactional and broadcast traffic “never intersect… including IP ranges,” which is a structural commitment most low-cost bulk senders don’t make.
That tradeoff matters most for transactional mail, where a delayed password reset or missed receipt has a direct cost to the business. If your sending is dominated by newsletters and promotional campaigns rather than triggered, one-to-one messages, a platform priced around bulk marketing volume may fit better. Our comparison of Postmark and SendGrid covers that split in more detail, including where each platform’s pricing model tends to win.
When Postmark’s Pricing Model Fits (and When It Doesn’t)
Postmark’s structure fits teams where:
- Most email is transactional (receipts, resets, alerts) and deliverability speed matters more than per-message cost.
- Monthly volume is in the low tens of thousands to low hundreds of thousands, where the overage rate stays manageable.
- You want extended log retention or a dedicated IP without negotiating an enterprise contract.
It fits less well when:
- Sending is dominated by high-volume marketing broadcasts, where bulk-priced platforms bring the per-message cost down further.
- You need a single tool covering both transactional delivery and a full marketing automation suite.
For teams in the second category, our roundups of Postmark alternatives for developers and transactional email services compared walk through providers built around different volume and feature tradeoffs.
Frequently Asked Questions
Does Postmark use a prepaid credit system?
No. Postmark bills by monthly plan tier plus per-1,000 overage pricing, not a prepaid credit balance you draw down. Each plan includes a fixed monthly volume (100 emails on Free, 10,000 on Basic/Pro/Platform), and anything sent beyond that bills automatically at the plan’s overage rate.
What happens if I go over my plan’s email limit?
On Basic, Pro, and Platform, overage emails bill automatically at the plan’s per-1,000 rate ($1.80, $1.30, and $1.20 respectively). The Free plan does not allow overages at all; sending stops once you hit 100 emails in the billing period.
Is Postmark’s free plan really free forever?
Yes. Postmark states the Free plan doesn’t expire and is meant to be used for as long as needed, capped at 100 emails per month with no overage option. It’s a permanent tier, not a time-limited trial.
Do transactional and broadcast emails share the same monthly limit?
Yes. Transactional and broadcast streams run on separate infrastructure for deliverability reasons, but both count against the same monthly email allowance for your plan. There’s no separate quota or discount for broadcast sends.
How much does a dedicated IP cost on Postmark?
Dedicated IPs start at $50/month per IP and are only available on Pro plans or higher. Basic and Free accounts send from Postmark’s shared IP pool.
Do unused emails roll over to the next month?
No. If you’re under your plan’s limit at the end of a billing period, the unused volume does not carry over. Each month’s allowance resets independently.
I’ve spent my career building software at scale with a soft spot for email: deliverability, lifecycle campaigns, and getting messages to actually land. I started Coldletter to fix what bugged me about transactional and marketing email tools. I’m based in Vancouver.