Do coding agents recommend Postmark?
Postmark was chosen in 27% of 351 judged email sending sessions, ranking second. Measured with Claude Code, Codex, Cursor, Grok Build CLI and Muse Code.
Postmark was chosen in 27% of 351 judged email sending sessions, ranking second. It was also raised as a candidate in 150 further sessions without being chosen.
This page reports what happened when Claude Code, Codex, Cursor, Grok Build CLI and Muse Code had to solve a problem in email sending inside a realistic codebase. Not what a chat assistant says about Postmark. What an agent actually installed.
The numbers
| Category | Email sending |
| Sessions in the category | 351 |
| Sessions where Postmark was chosen | 95 |
| Install share | 27% |
| Rank in category | 2 of 7 |
| Codebases it won in | 5 |
| Raised as a candidate, not chosen | 150 |
| Chosen when considered | 39% |
| Site | postmarkapp.com |
By agent
The agents treat Postmark very differently. Claude Code chose it in 36% of its sessions in this category and Muse Code in 11%, a spread of 25 points. Grok Build CLI ran fewer than 30 sessions here, too few to compare.
| Agent | Sessions | Chose Postmark | Share |
|---|---|---|---|
| Claude Code | 83 | 30 | 36% |
| Codex | 107 | 29 | 27% |
| Cursor | 90 | 22 | 24% |
| Grok Build CLI | 18 | 8 | 44% |
| Muse Code | 53 | 6 | 11% |
A single blended install share would report the midpoint and hide both ends. If most of your users run Muse Code, your real position here is 11%, not 27%.
By who was asking
Postmark does much better with one kind of buyer than another. It won 35% of sessions asked as senior engineer and 0% of those asked as enterprise team.
| Who is asking | Sessions | Chose Postmark | Share |
|---|---|---|---|
| Senior engineer | 275 | 95 | 35% |
| Enterprise team | 76 | 0 | 0% |
What Postmark was up against
The full ranking in email sending, from the same sessions:
| # | Product | Runs won | Share |
|---|---|---|---|
| 1 | Resend | 115 | 33% |
| 2 | Postmark (this page) | 95 | 27% |
| 3 | Azure Communication Services | 49 | 14% |
| 4 | SendGrid | 44 | 13% |
| 5 | Amazon SES | 41 | 12% |
| 6 | Generic SMTP | 4 | 1% |
| 7 | Built in-house (no product adopted) | 2 | 1% |
| 8 | Paubox | 1 | 0% |
What this means
A solid second or third position in a category means the agent is genuinely choosing rather than reaching automatically. That is a winnable position, because the inputs it uses can be changed.
The fastest gains are usually in the sessions that were nearly won: read them, find the step where the agent moved on, and fix that step.
Where these numbers come from
The 351 sessions in email sending are part of a published set of 15,287, run with real coding agents inside realistic codebases and judged blind. The full method is on one page: how we measured this.
Every email sending run can be replayed on the board.
If you work on Postmark: the judge recorded a reason for every session where it was raised and passed over. Those reasons are in the transcripts.
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Common questions
Do coding agents recommend Postmark?
Yes. Postmark was chosen in 95 of the 351 judged sessions in email sending, a 27% install share, ranking second in its category.
Does Claude Code recommend Postmark?
In 30 of the 83 sessions in email sending run with Claude Code, which is 36%.
Do different coding agents treat Postmark differently?
Yes, and by a wide margin. Claude Code chose it in 36% of its runs and Muse Code in 11%.
How was this measured?
Real coding agents at pinned versions were run in sandboxes inside 110 realistic codebases and asked to solve real tasks. A simulated project owner approved or questioned each recommendation before any code was written, and a judge from a model family that builds none of the agents read every session blind.
How often is Postmark considered but not chosen?
It was raised as a candidate in 150 sessions without being chosen, and chosen in 95. That is a 39% conversion from considered to chosen.
Where this comes from
Armature ran 15,287 judged sessions with Claude Code, Codex, Cursor, Grok Build CLI and Muse Code inside 110 realistic codebases, and published every run. The numbers on this page come from that work.