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 mailgun/mailgun-plugins --skill missing-email-investigationgit clone --depth 1 https://github.com/mailgun/mailgun-pluginsWrote 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/mailgun/mailgun-plugins/missing-email-investigation)<a href="https://agentmods.dev/skills/mailgun/mailgun-plugins/missing-email-investigation"><img src="https://agentmods.dev/badge/skills/mailgun/mailgun-plugins/missing-email-investigation/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/mailgun/mailgun-plugins/missing-email-investigation"><img src="https://agentmods.dev/badge/skills/mailgun/mailgun-plugins/missing-email-investigation.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00033 | $0.00487 |
| Opus 5 | $0.00016 | $0.00244 |
| Sonnet 5 | $0.00007 | $0.00097 |
| Haiku 4.5 | $0.00003 | $0.00049 |
Grade A, and why
missing-email-investigation 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 8d 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 — 42 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Missing Email Investigation
Use this skill when the user asks why a specific email did not arrive, whether a recipient got a message, or what happened to a message for a recipient in a known time window.
Use post send analysis for a campaign or tag level review. Use deliverability triage for broad domain or reputation issues.
Intake
Ask for domain, region, recipient address, approximate send time or time range, and any available message ID, storage key, subject, tag, or template name.
Workflow
- Confirm the active region and domain before searching.
- Query logs for the recipient, message ID, tag, subject, or time window using the narrowest available filter.
- Build a timeline from accepted, delivered, opened, clicked, temporary failure, permanent failure, complained, unsubscribed, stored, or dropped events when available.
- Check bounce, unsubscribe, complaint, and allowlist state for the recipient.
- Retrieve stored message metadata or resend context only when it helps explain the timeline.
- Classify the likely outcome: delivered, still retrying, suppressed, bounced, rejected by provider, blocked by policy, failed due to template/content, or not found in the chosen window.
- Return a plain language explanation, evidence table, confidence level, and the next safe action.
Interpretation
- Accepted or queued is not proof of delivery. Check later log events.
- Suppressed recipients can make later sends appear to vanish without a request error.
- Temporary failures may retry before final delivery or final failure.
- A missing result can mean the wrong region, wrong domain, too narrow a time window, or a send that never reached Mailgun.
- Provider messages and SMTP responses are evidence, but should be summarized carefully and not over interpreted.
Safety
Keep the investigation diagnostic unless the user explicitly asks for remediation. Do not resend a message, remove a suppression, add an allowlist entry, or change account settings without confirmation of the domain, recipient, message, and expected consequence.
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.
- 8d ago First seen · 42 lines · 33 tokens per session scan A e3601469b8c1
missing-email-investigation is a skill published in the GitHub repository mailgun/mailgun-plugins (1 stars, last pushed 19d ago), licensed Apache-2.0. It adds 33 tokens to every session and 487 once invoked, about $0.0002 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 2026-08-31.
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