Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add ActiveCampaign/postmark-skills --skill postmark-email-best-practicesgit clone --depth 1 https://github.com/ActiveCampaign/postmark-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/activecampaign/postmark-skills/postmark-email-best-practices)<a href="https://agentmods.dev/skills/activecampaign/postmark-skills/postmark-email-best-practices"><img src="https://agentmods.dev/badge/skills/activecampaign/postmark-skills/postmark-email-best-practices/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/activecampaign/postmark-skills/postmark-email-best-practices"><img src="https://agentmods.dev/badge/skills/activecampaign/postmark-skills/postmark-email-best-practices.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00055 | $0.01164 |
| Opus 5 | $0.00028 | $0.00582 |
| Sonnet 5 | $0.00011 | $0.00233 |
| Haiku 4.5 | $0.00006 | $0.00116 |
Grade A, and why
postmark-email-best-practices scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 110 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Email Best Practices
Postmark has delivered billions of transactional emails over 15+ years. This skill distills that expertise into actionable guidelines for building reliable, compliant, high-deliverability email systems.
Quick Reference
| Topic | Use When |
|---|---|
| Deliverability | Setting up SPF/DKIM/DMARC, warming a new domain, diagnosing delivery issues |
| Compliance | Building unsubscribe flows, handling GDPR/CAN-SPAM/CASL requirements |
| Transactional Design | Designing welcome emails, password resets, receipts, alerts |
| List Management | Handling bounces, suppressions, list hygiene |
| Testing | Testing safely without hurting sender reputation |
| Sending Reliability | Idempotency, retry logic, rate limits |
Deliverability Fundamentals
The three authentication records every sending domain must have:
| Record | Purpose | Priority |
|---|---|---|
| SPF | Authorizes servers to send as your domain | Required |
| DKIM | Cryptographically signs emails to prove authenticity | Required |
| DMARC | Policy for handling SPF/DKIM failures | Required |
With Postmark, DKIM is configured automatically when you verify a sender domain. SPF and DMARC must be set up in your DNS.
See references/deliverability.md for DNS setup, reputation factors, and domain warm-up guidance.
Transactional vs. Broadcast Email
Never mix transactional and broadcast email in the same sending stream. They have different delivery characteristics, compliance requirements, and reputation profiles.
| Type | Examples | Compliance | Unsubscribe Required |
|---|---|---|---|
| Transactional | Password resets, receipts, alerts, notifications | CAN-SPAM exemption possible | No (but good practice) |
| Broadcast | Newsletters, promotions, announcements | CAN-SPAM, GDPR, CASL apply | Yes — legally required |
Postmark enforces this separation with Message Streams — use outbound for transactional, broadcast for marketing.
What ships with it
6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 10d ago First seen · 110 lines · 55 tokens per session scan A 7f0070352e6e
postmark-email-best-practices is a skill published in the GitHub repository ActiveCampaign/postmark-skills (46 stars, last pushed 22d ago), licensed MIT. It adds 55 tokens to every session and 1,164 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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