Documentation Mailgun Mailgun API
41
AI ReadinessFoundational (D-)41/100
Official vendor OpenAPI document · agent-readyCommunicationsEmail Deliverybasic2 EndpointsREST
For Agents
Send a transactional email via Mailgun and retrieve the stored message by its ID using HTTP Basic authentication with a private API key.
Use for: I need to send a transactional email through Mailgun, Send an order confirmation email to a customer, Retrieve a previously sent message by its messageId, Send a verification email with an HTML body
Not supported: Does not handle SMS, push notifications, or voice calls - use for transactional email delivery and stored-message retrieval only.
The Mailgun API is a transactional email delivery service that lets developers send messages and retrieve delivery details through a simple REST interface. This Jentic-curated specification exposes the two core operations: POST /{domain}/messages to send an email and GET /{domain}/messages/{messageId} to fetch a stored message by ID. Authentication uses HTTP Basic with the Mailgun private API key as the password. The API is suited to teams sending application-generated email such as receipts, notifications, and verification messages from a verified sending domain.
Install Jentic One Beta
Connect the Mailgun API to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the Mailgun API, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
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Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fdocumentation.mailgun.com%2Fmailgun" | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fdocumentation.mailgun.com%2Fmailgun" | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with Mailgun API.
Send a transactional email through POST /{domain}/messages
Retrieve a stored message by ID via GET /{domain}/messages/{messageId}
Address messages to multiple recipients in a single send
Attach files and inline images to outbound messages
Authenticate every call with HTTP Basic and the Mailgun private API key
Use Cases
Patterns agents use Mailgun API for, with concrete tasks.
★ Transactional Email Delivery
Send transactional emails such as receipts, password resets, and account notifications by posting to /{domain}/messages with from, to, subject, and body fields. Mailgun handles routing, retries, and delivery tracking on the configured sending domain. Integrating the single send endpoint typically takes under an hour.
POST /{domain}/messages with from='noreply@example.com', to='user@example.com', subject='Receipt', and an HTML body, then capture the returned message id.
Message Retrieval and Audit
Fetch a stored email by its message ID via GET /{domain}/messages/{messageId} to support audit logs, customer support lookups, and content review. The endpoint returns the original message body and headers so an agent or support tool can reproduce what was sent without storing the content separately.
GET /{domain}/messages/{messageId} for a known message id and parse the response body to confirm the recipient and subject line.
AI Agent Notifications via Jentic
An AI agent calls Mailgun through Jentic to dispatch transactional notifications (alerts, summaries, status updates) on behalf of users. The agent searches Jentic for 'send an email', loads the schema for POST /{domain}/messages, and executes the call while Jentic injects the Mailgun Basic auth credential.
Search Jentic for 'send a transactional email', load the Mailgun POST messages operation, and execute it to notify a user that a long-running task has finished.
Key Endpoints
2 endpoints — the mailgun api is a transactional email delivery service that lets developers send messages and retrieve delivery details through a simple rest interface.
METHOD
PATH
DESCRIPTION
POST
/{domain}/messages
Send an email message
GET
/{domain}/messages/{messageId}
Get message details by ID
POST
/{domain}/messages
Send an email message
GET
/{domain}/messages/{messageId}
Get message details by ID
Jentic AI Readiness Score
This API is usable in Jentic One now. Its AI-readiness score against Jentic's framework shows where it stands today and where improvements would make it even easier for agents to use.
M
Mailgun API
- Foundational (D-)41/100
100
Foundational Compliance63
Developer Experience & Jentic Compatibility52
AI-Readiness & Agent Experience94
Agent Usability10
Security100
AI DiscoverabilityPowered by JenticScoring Framework 1.0.0 | Scoring Engine 0.4.0
Show dimension breakdown
100
Foundational Compliance
Base layer of spec validity and structural soundness.
Grade: A+Signals: 4
99%
Lint Results
Aggregated quality score from linter diagnostics, weighted by severity.
100%
Resolution Completeness
Percentage of `$ref` references that resolve successfully.
100%
Specification Validity
Checks whether the API description parses successfully and conforms to its declared specification (e.g., OpenAPI).
100%
Structural Integrity
Structural correctness score based on schema issues using logarithmic dampening.
63
Developer Experience & Jentic Compatibility
Clarity, completeness, and ingestion readiness for developers and tooling.
Grade: B-Signals: 4
0%
Example Density
How richly the API is illustrated with examples.
100%
Example Validity
Percentage of examples that conform to their schemas.
50%
Response Coverage
Percentage of operations with complete response definitions (success, client error, server error).
100%
Tooling Readiness
Health of API ingestion, bundling, and resolution within Jentic pipelines.
52
AI-Readiness & Agent Experience
Semantic breadth, depth, and agent comprehension for AI systems.
Grade: C-Signals: 4
57%
Description Coverage
Coverage of descriptions across API elements.
0%
Error Standardization
Coverage of RFC 9457 Problem Details for error responses.
100%
OperationId Quality
Coverage, uniqueness, and casing consistency of operationIds for AI inference.
50%
Summary Coverage
Coverage of summaries across operations/tags/info.
94
Agent Usability
Functional utility, complexity comfort, and AI orchestration readiness.
Grade: A+Signals: 1
94%
Complexity Comfort
Agent comfort level based on API operational and structural complexity.
10
Security
Trust, risk posture, and security compliance.
Grade: FSignals: 1
10%
Authentication Strength
Average quality of security schemes based on authentication method strength (weakest link for OAuth2).
100
AI Discoverability
Findability, semantic richness, and reasoning readiness.
Grade: A+Signals: 1
100%
Descriptive Richness
Clarity and depth of descriptions across API elements.
Score it yourself
Every API in the directory is allowlisted, so you can re-score it with no key required.
npx @jentic/api-scorecard-cli score <openapi-url>Why Jentic?
What agents get from Jentic-routed access to this vendor.
Setup
Wiring the Mailgun API by hand means encoding your private key into a Basic auth header and slotting your verified sending domain into each route before a message sends. Through Jentic you install once, import the Mailgun API from the API Directory, store the private key once, and your agent calls it.
Permission scoping
Mailgun puts the sending domain in the URL path (/{domain}/messages), so a rule can pin your agent to one domain: it can send and retrieve stored messages for that domain and nothing else. You choose the operations it may call, so it sends only from the domain and endpoints you allow.
Credential isolation
Your Mailgun private API key is stored once, encrypted, by your own Jentic One instance and injected at execution time. It never enters the agent's prompt, logs, or context.
Intent-based discovery
Agents search Jentic by intent such as 'send a transactional email', and Jentic returns the Mailgun POST /{domain}/messages operation with its parameter schema so the agent calls the right endpoint against the verified sending domain without reading the reference docs.
Related APIs
Alternatives and complements available in the Jentic catalogue.
FAQs
Specific to using Mailgun API through Jentic.
What authentication does the Mailgun API use?
Mailgun uses HTTP Basic authentication. You pass the literal string 'API' as the username and your Mailgun private API key as the password. Through Jentic, the key is stored encrypted in the vault and applied at execution time so the agent runtime never holds it.
Can I send a transactional email with the Mailgun API?
Yes. POST /{domain}/messages accepts from, to, subject, and text or html body fields and queues the message for delivery from your verified sending domain. The response contains the Mailgun message id you can store for later retrieval.
What are the rate limits for the Mailgun API?
Limits depend on your Mailgun plan and the reputation of your sending domain rather than a single per-second cap declared in the spec. Apply exponential backoff on 429 responses and respect the per-domain hourly limits visible in the Mailgun control panel.
How do I send an email with the Mailgun API through Jentic?
Run pip install jentic and search for 'send a transactional email'. Jentic returns the Mailgun POST /{domain}/messages operation with its parameter schema. Execute it with from, to, subject, and body; Jentic injects the Basic auth credential automatically.
Can I retrieve a previously sent message?
Yes. GET /{domain}/messages/{messageId} fetches the stored message body and headers for a given Mailgun message id. This supports audit, replay, and customer support flows without keeping a separate copy of the email content.
Does the Mailgun API support multiple recipients?
Yes. POST /{domain}/messages accepts a comma-separated list in the to field and supports cc and bcc. For larger sends, batch through Mailgun recipient variables to keep each request within Mailgun's recipient limits.
Can I limit what my agent is allowed to do with the Mailgun API?
Yes. Because you run Jentic One yourself, your own rules decide which Mailgun operations and credentials the agent may use. Since Mailgun puts the sending domain in the URL path (/{domain}/messages), you can pin the agent to a single verified domain and grant only the operations you choose, such as sending via POST /{domain}/messages while withholding message retrieval, or the reverse. Anything you do not allow stays off limits to the agent.
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