Postmark is a transactional-first delivery service that runs its own sending infrastructure and keeps transactional mail on a stream of its own; that reputation is the reason people pay for it. Notix is a transactional and marketing platform on one suppression list, with an OTP API and a pre-send deliverability check, at $15 a month for 50,000 emails where Postmark's $15 buys 10,000. One is a delivery specialist; the other bundles more around the send.
Postmark's figures were read from its pricing page on 2026-09-13; the date is repeated under the table. Notix figures come from its own pricing page.
| Criterion | Postmark | Notix |
|---|---|---|
| Free tier | 100 emails a month on the developer plan | 5,000 emails a month, 200 a day, no card, no end date |
| Entry paid plan | Basic $15 a month | Pro $15 a month |
| Included on that plan | 10,000 emails a month, then $1.80 per extra 1,000 | 50,000 emails, usage past that metered on the same invoice |
| SMTP relay | Yes, on every plan | Yes, on every plan |
| SDKs | Node, Python, Ruby, PHP, .NET, and a documented cURL surface | TypeScript, Python, Go, PHP |
| Webhooks | Yes | Yes, signed, for email, contact and domain events |
| OTP / verification API | No | Yes, email and SMS codes |
| Deliverability check before sending | No | Yes, a pre-send check API |
| Billing outside USD | USD by card | USD by card; naira and shillings from a prepaid wallet |
| SLA | Not stated on the pricing page | 99.9% on Pro, credits on the pricing page |
| Prices and limits read from the vendors' own pages: postmarkapp.com on 2026-09-13. Notix figures are from its own pricing page. | ||
Postmark's developer plan is 100 emails a month, enough to test with. Basic is $15 a month for 10,000 emails and $1.80 for each extra 1,000, so 50,000 emails cost about $87 and 100,000 about $177, unless you move to a larger plan. Notix Free is 5,000 emails a month and 200 a day with no card and no end date; Pro is $15 for 50,000 emails, with usage past that metered on the same invoice at the rate on the pricing page. At the $15 line the volume difference is five to one.
Both take a JSON body with from, to, subject and html and return a message id. Postmark adds a message stream field so transactional and broadcast mail travel separately, and offers batch sending of up to 500 messages per call. Notix accepts an idempotency key on every send so a retry cannot double-deliver, and has batch and scheduled sends on the same endpoint family; its email API also covers contacts, templates and campaigns under one key. A plain transactional send moves between them after a client swap.
Postmark's answer is its infrastructure: its own IPs, stream separation and a public time-to-inbox record. Notix does not contest that and makes no infrastructure claim of its own. What Notix adds is tooling around the send: a deliverability check you call before sending, which returns a score and the findings that would block delivery, and a suppression list shared across transactional and marketing mail. The transactional email API page describes both. Both verify domains with SPF, DKIM and DMARC and report bounces and complaints.
Postmark's broadcast stream sends one-to-many mail, but list management, sign-up forms, double opt-in and automation are not part of the product; teams pair it with a separate marketing tool. Notix has contact books with double opt-in, a template editor, campaigns and journeys in the same account as transactional sending, and every kind of mail shares one suppression list, so an address that bounced a newsletter never receives a receipt. If you want one vendor for both kinds of mail, this row decides it.
Postmark publishes official libraries for Node, Python, Ruby, PHP and .NET, plus a documented cURL surface, and its documentation is thorough for each. Notix publishes TypeScript, Python, Go and PHP, and everything else uses the JSON endpoint with a plain HTTP client, as the docs show for curl. Ruby and .NET teams get a typed client from Postmark and not from Notix; Go teams get one from Notix and not from Postmark. For the languages both cover, the clients are interchangeable in shape.
Postmark sends the email you compose; generating a code, storing it, expiring it and checking the user's answer are yours to build. Notix has a verification API that does all four in two calls, by email or by SMS, with a risk score on the request. If sign-in or sign-up codes are part of your product, this is a real difference between the two; if you never send a code, it is a row you can skip.
Postmark bills in US dollars by card. Notix bills in US dollars by card too, and additionally lets teams in Nigeria and Kenya fund a prepaid wallet in naira or shillings, from which Pro is charged each month, so a card that clears international charges is not required. Plan prices are the same everywhere; only the currency and the payment method differ. If you bill from Lagos or Nairobi, this is often the deciding row.
Notix states a 99.9 percent uptime commitment on Pro, with the credit schedule written on the pricing page; the free plan is best effort. Postmark's pricing page does not state an SLA figure for Basic, so this page does not put one in its mouth; its status page publishes uptime and delivery times historically. Both offer email support; neither publishes response times on the plans compared here.
Already decided? The switching from Postmark page has the SDK and SMTP swap and the suppression import.
Five times the included volume at the same $15, with the marketing side and an OTP API in the same account.
NotixA free plan with no card, and Pro at $15 a month for 50,000 emails. Only sent volume is metered.
ProductOTPs, receipts and alerts with idempotency keys, a deliverability pre-check and a shared suppression list.
CompareEvery vendor in one table with read dates, and a straight answer to which transactional email API a startup should pick.
CompareSame $15 entry, different included volume, and where Mailgun's inbound routing and validation matter.
5,000 emails a month on Free, no card, no end date. Pro is $15 for 50,000 emails, by card or from a naira or shilling wallet.