Warming up
Transactional email API
Warmerly is a cheaper Postmark alternative once you send more than 10,000 emails a month: $15 for 50,000 against $55 on Postmark Basic, and $29 for 100,000 against $115. At 10,000 both cost $15. Like Postmark, it keeps transactional mail away from bulk mail. Postmark is the better pick if you need SMTP, templates, webhooks, inbound email or 45 days of full message history.
Postmark separates transactional and broadcast email with message streams inside one account. Warmerly keeps its transactional API as a separate product that only sends app email, and never sends outreach through it.
Honestly, in these cases we would stay with Postmark.
Compared with Postmark Basic, the cheapest of its three paid plans. At 10,000 emails the two cost the same; above that, Warmerly's larger allowances pull ahead. Postmark's 100,000 price is its 125,000 step, since it has no 100,000 plan.
| Emails a month | Warmerly | Postmark |
|---|---|---|
| 10,000 | $15Starter | $15Basic 10k |
| 50,000 | $15Starter | $55Basic 50k |
| 100,000 | $29Growth | $115Basic 125k |
| 500,000 | $279Scale 500k | $455Basic 700k |
List prices, monthly billing, USD: the cheapest published plan that includes that many emails, overage left out on both sides. Postmark prices from postmarkapp.com as of September 2026; check their site for current rates. Shaded cells are the cheaper side.
What each one does today. Where Warmerly says "not yet", it means it: those are on the roadmap, not built.
| Feature | Warmerly | Postmark |
|---|---|---|
| API shape | REST, JSON over HTTPS, bearer key, Idempotency-Key header | REST, POST /email with PascalCase fields; server token header |
| SMTP relay | Not yet (on the roadmap) | Yes |
| Delivery webhooks | Not yet. Read each email's delivery timeline from GET /emails/{id} | Yes |
| Templates | Not yet. You send your own HTML and text | Yes |
| Dedicated IP | $29/mo on Scale plans | From $50/mo, for 300,000+ emails a month on Pro or higher |
| Suppression list | Automatic on hard bounce and spam complaint, shared with Warmerly outreach | Automatic on hard bounce and spam complaint, per message stream |
| Free tier | 5,000 a month (200 a day), no time limit, no card | 100 emails a month |
| Log retention | Content 30 days; the email record and its delivery events are kept | 45 days; up to 365 on Pro and Platform (add-on from $5/mo) |
| SDKs | None. One HTTP request from any language | Official libraries for several languages (see postmarkapp.com) |
| Support | Email (support@warmerly.com), plus a 99.9% monthly uptime commitment with service credits | See postmarkapp.com |
Most of the work is DNS. The code change is small, but it is a change.
Add the domain and publish the DKIM CNAMEs, bounce MX, SPF and DMARC records it shows. Postmark's DKIM and Return-Path records can stay until you switch.
POST to https://app.warmerly.com/api/v1/transactional/emails with Authorization: Bearer wm_tx_... instead of X-Postmark-Server-Token.
The table above maps each one. Recipients become a string or a list instead of a comma-separated string; Headers become an object.
Warmerly has no template store. Render the HTML where you build the email today and send html and text.
There is nothing to pick: everything sent through this API is transactional, and Warmerly keeps it apart from outreach for you.
| Postmark | Warmerly |
|---|---|
| X-Postmark-Server-Token | Authorization: Bearer wm_tx_... |
| POST /email | POST /api/v1/transactional/emails |
| From | from |
| To: "a@x.com, b@y.com" | ["a@x.com", "b@y.com"] |
| Cc, Bcc | cc, bcc |
| ReplyTo | reply_to |
| Subject | subject |
| HtmlBody | html |
| TextBody | text |
| Headers: [{ Name, Value }] | headers: { name: value } |
| Tag, Metadata | tags |
| MessageStream | (not needed) |
Above 10,000 emails a month, yes, on list prices as of September 2026: $15 against $55 for 50,000, $29 against $115 for 100,000 (Postmark's 125k step), and $279 against $455 for 500,000. At 10,000 both are $15.
Not as a setting. Postmark separates transactional and broadcast mail with streams inside one account. Warmerly separates them by product: the transactional API only sends app email, on SES tenants of its own, and Warmerly's cold outreach and warmup run on your own mailboxes and never touch it.
Each email's content (html and text) is kept for 30 days and then cleared. The email record and its delivery events stay. Postmark keeps 45 days of activity by default.
5,000 emails a month, up to 200 a day, with no time limit and no card. Postmark's free developer plan is 100 emails a month.
No. The field names and endpoint are different. The change is small (a table of renamed fields), but it is a code change.
Create a free account, verify a sending domain and send a test from the dashboard. 5,000 emails a month free, no card.
