AgentMailer MCP

• Outcome: Pass
• Latest audit: Sep 16, 2026 · 11:19 AM UTC
• Version: 0.4.0

Overview

This skill is a disclosed AgentMailer MCP setup and troubleshooting guide with expected OAuth and remote service use, not hidden or destructive behavior.

Install this only if you intend to connect your agent client to AgentMailer. Expect a persistent remote MCP configuration and OAuth authorization flow; review the permissions returned by auth_me before creating inboxes or enabling direct agent communication.

A.I.G

Vulnerability Patterns

• Skill Instruction Hijacking: Alters the agent's session goals or safety constraints when the skill loads
• Agent Memory Poisoning: Writes attacker-controlled rules into memory that affect later sessions
• Remote Payload Retrieval and Execution: Fetches external code whose behavior can change after review
• Embedded Malicious Code: Ships malicious scripts inside the skill and executes them locally
• Unauthorized Access and Privilege Escalation: Obtains permissions beyond the task's legitimate needs

SkillSpector

Vulnerability Patterns

• Data Exfiltration: External Transmission, Env Variable Harvesting, File System Enumeration
• Privilege Escalation: Excessive Permissions, Sudo/Root Execution, Credential Access
• Excessive Agency: Unrestricted Tool Access, Autonomous Decision Making, Scope Creep
• Prompt Injection: Instruction Override, Hidden Instructions, Exfiltration Commands
• Supply Chain: Unpinned Dependencies, External Script Fetching, Obfuscated Code

Findings (12)

Credential Access

High

• Category: Privilege Escalation
• Confidence: 70% confidence

Finding

Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Content

Scanner excerpt · references/troubleshooting.md (reported line 22)May include surrounding context.

md

6. Call `list_inboxes`. An empty result is valid and is not a transport failure.
7. If a tool returns `forbidden`, compare the requested operation with the permissions returned by `auth_me`; do not retry with guessed organization or resource identifiers.

Treat `401` as missing or invalid authentication and `403` as authenticated but unauthorized. `human_approval_required` specifically means the approval ceremony is incomplete. Do not expose access tokens, authorization headers, approval codes, or reviewer credentials in diagnostics.

Autonomous Decision Making

Medium

• Category: Excessive Agency
• Confidence: 80% confidence

Finding

Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.

Content

Scanner excerpt · SKILL.md (reported line 12)May include surrounding context.

md

`https://api.agentmailer.ai/mcp`

Prefer the client's native remote-MCP configuration so it can discover OAuth from AgentMailer's protected-resource metadata. Do not ask the user to paste OAuth tokens into prompts, source files, or shell history.

## Connect

External Transmission

Medium

• Category: Data Exfiltration
• Confidence: 50% confidence

Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · SKILL.md (reported line 10)May include surrounding context.

md

## Public endpoints

- MCP: `https://api.agentmailer.ai/mcp`
- OAuth protected-resource metadata: `https://api.agentmailer.ai/.well-known/oauth-protected-resource`
- Canonical signup and connection guide: `https://api.agentmailer.ai/llms.txt`
- AgentMailer authentication guide: `https://api.agentmailer.ai/auth.md`

External Transmission

Medium

• Category: Data Exfiltration
• Confidence: 50% confidence

Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · SKILL.md (reported line 18)May include surrounding context.

md

## Public endpoints

- MCP: `https://api.agentmailer.ai/mcp`
- OAuth protected-resource metadata: `https://api.agentmailer.ai/.well-known/oauth-protected-resource`
- Canonical signup and connection guide: `https://api.agentmailer.ai/llms.txt`
- AgentMailer authentication guide: `https://api.agentmailer.ai/auth.md`

External Transmission

Medium

• Category: Data Exfiltration
• Confidence: 50% confidence

Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · SKILL.md (reported line 19)May include surrounding context.

md

## Public endpoints

- MCP: `https://api.agentmailer.ai/mcp`
- OAuth protected-resource metadata: `https://api.agentmailer.ai/.well-known/oauth-protected-resource`
- Canonical signup and connection guide: `https://api.agentmailer.ai/llms.txt`
- AgentMailer authentication guide: `https://api.agentmailer.ai/auth.md`

External Transmission

Medium

• Category: Data Exfiltration
• Confidence: 50% confidence

Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · SKILL.md (reported line 23)May include surrounding context.

md

## Public endpoints

- MCP: `https://api.agentmailer.ai/mcp`
- OAuth protected-resource metadata: `https://api.agentmailer.ai/.well-known/oauth-protected-resource`
- Canonical signup and connection guide: `https://api.agentmailer.ai/llms.txt`
- AgentMailer authentication guide: `https://api.agentmailer.ai/auth.md`

External Transmission

Medium

• Category: Data Exfiltration
• Confidence: 50% confidence

Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · SKILL.md (reported line 33)May include surrounding context.

md

## Public endpoints

- MCP: `https://api.agentmailer.ai/mcp`
- OAuth protected-resource metadata: `https://api.agentmailer.ai/.well-known/oauth-protected-resource`
- Canonical signup and connection guide: `https://api.agentmailer.ai/llms.txt`
- AgentMailer authentication guide: `https://api.agentmailer.ai/auth.md`

External Transmission

Medium

• Category: Data Exfiltration
• Confidence: 50% confidence

Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · agents/openai.yaml (reported line 11)May include surrounding context.

yaml

## Public endpoints

- MCP: `https://api.agentmailer.ai/mcp`
- OAuth protected-resource metadata: `https://api.agentmailer.ai/.well-known/oauth-protected-resource`
- Canonical signup and connection guide: `https://api.agentmailer.ai/llms.txt`
- AgentMailer authentication guide: `https://api.agentmailer.ai/auth.md`

External Transmission

Medium

• Category: Data Exfiltration
• Confidence: 50% confidence

Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · references/troubleshooting.md (reported line 5)May include surrounding context.

md

## Public endpoints

- MCP: `https://api.agentmailer.ai/mcp`
- OAuth protected-resource metadata: `https://api.agentmailer.ai/.well-known/oauth-protected-resource`
- Canonical signup and connection guide: `https://api.agentmailer.ai/llms.txt`
- AgentMailer authentication guide: `https://api.agentmailer.ai/auth.md`

External Transmission

Medium

• Category: Data Exfiltration
• Confidence: 50% confidence

Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · references/troubleshooting.md (reported line 6)May include surrounding context.

md

## Public endpoints

- MCP: `https://api.agentmailer.ai/mcp`
- OAuth protected-resource metadata: `https://api.agentmailer.ai/.well-known/oauth-protected-resource`
- Canonical signup and connection guide: `https://api.agentmailer.ai/llms.txt`
- AgentMailer authentication guide: `https://api.agentmailer.ai/auth.md`

External Transmission

Medium

• Category: Data Exfiltration
• Confidence: 50% confidence

Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · references/troubleshooting.md (reported line 7)May include surrounding context.

md

## Public endpoints

- MCP: `https://api.agentmailer.ai/mcp`
- OAuth protected-resource metadata: `https://api.agentmailer.ai/.well-known/oauth-protected-resource`
- Canonical signup and connection guide: `https://api.agentmailer.ai/llms.txt`
- AgentMailer authentication guide: `https://api.agentmailer.ai/auth.md`

External Transmission

Medium

• Category: Data Exfiltration
• Confidence: 50% confidence

Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · references/troubleshooting.md (reported line 8)May include surrounding context.

md

## Public endpoints

- MCP: `https://api.agentmailer.ai/mcp`
- OAuth protected-resource metadata: `https://api.agentmailer.ai/.well-known/oauth-protected-resource`
- Canonical signup and connection guide: `https://api.agentmailer.ai/llms.txt`
- AgentMailer authentication guide: `https://api.agentmailer.ai/auth.md`