# Do coding agents recommend Postmark?

> Postmark was chosen in 27% of 208 judged email sending sessions, ranking second. Measured with Claude Code, Codex and Cursor.

Source: https://armature.tech/library/do-coding-agents-recommend-postmark
Published: 2026-09-03
Publisher: Armature, Inc. (https://armature.tech)

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> Postmark was chosen in 27% of 208 judged email sending sessions, ranking second. It was also raised as a candidate in 112 further sessions without being chosen.

This page reports what happened when Claude Code, Codex and Cursor 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 | 208 |
| Sessions where Postmark was chosen | 57 |
| Install share | 27% |
| Rank in category | 2 of 6 |
| Codebases it won in | 5 |
| Raised as a candidate, not chosen | 112 |
| Chosen when considered | 34% |
| Site | postmarkapp.com |

## By agent

The three agents land within 13 points of each other on Postmark, which is closer than most products in this experiment manage.

| Agent | Sessions | Chose Postmark | Share |
| --- | --- | --- | --- |
| Claude Code | 65 | 23 | 35% |
| Codex | 71 | 18 | 25% |
| Cursor | 72 | 16 | 22% |

## 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 | 164 | 57 | 35% |
| Enterprise team | 44 | 0 | 0% |

## What Postmark was up against

The full ranking in email sending, from the same sessions:

| # | Product | Runs won | Share |
| --- | --- | --- | --- |
| 1 | Resend | 74 | 36% |
| 2 | Postmark **(this page)** | 57 | 27% |
| 3 | Azure Communication Services Email | 29 | 14% |
| 4 | Amazon SES | 24 | 12% |
| 5 | SendGrid | 23 | 11% |
| 6 | Generic SMTP | 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 208 sessions in email sending are part of a published set of 5,292, run with real coding agents inside realistic codebases and judged blind. The full method is on one page: [how we measured this](/library/how-we-measured-this).

Every email sending run can be replayed on [the board](/leaderboards/mail).

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 57 of the 208 judged sessions in email sending, a 27% install share, ranking second in its category.

### Does Claude Code recommend Postmark?

In 23 of the 65 sessions in email sending run with Claude Code, which is 35%.

### Do different coding agents treat Postmark differently?

Yes, and by a wide margin. Claude Code chose it in 35% of its runs and Cursor in 22%.

### How was this measured?

Real coding agents at pinned versions were run in sandboxes inside 51 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 112 sessions without being chosen, and chosen in 57. That is a 34% conversion from considered to chosen.

## Read next

- [How to get picked for email sending by coding agents](https://armature.tech/library/mail-coding-agents-playbook) (Markdown: https://armature.tech/library/mail-coding-agents-playbook.md)
- [Do coding agents recommend Resend?](https://armature.tech/library/do-coding-agents-recommend-resend) (Markdown: https://armature.tech/library/do-coding-agents-recommend-resend.md)
- [Do coding agents recommend Azure Communication Services Email?](https://armature.tech/library/do-coding-agents-recommend-azure-communication-services-email) (Markdown: https://armature.tech/library/do-coding-agents-recommend-azure-communication-services-email.md)
- [Do Claude Code, Codex and Cursor pick the same tools?](https://armature.tech/library/do-claude-code-and-codex-agree) (Markdown: https://armature.tech/library/do-claude-code-and-codex-agree.md)

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