Mailosaur API

Name: Mailosaur API API
Brand: Mailosaur API
Availability: InStock

✓ Official Vendor SpecDeveloper ToolsTesting Qabasic23 EndpointsREST

For Agents

Run end-to-end tests against email and SMS flows — search inbound messages on a Mailosaur server, inspect content and spam analysis, and forward or reply for round-trip assertions across 23 endpoints.

Quickstart

Get started with Mailosaur API in minutes using your preferred integration method.

# Add to your MCP client config (Claude Desktop, Cursor, Windsurf)
{
  "jentic": {
    "url": "https://api.jentic.com/mcp",
    "auth": "oauth"
  }
}

# Then ask your agent:
"search captured emails on mailosaur"

# → Jentic returns the GET /events tool with parameter schema, agent executes.

Capabilities

What an agent can do with Mailosaur API API.

Provision and delete virtual mail servers for isolated test environments

Search inbound messages by sender, subject, or body content

Inspect a delivered message including HTML, text, and attachments

Run spam analysis against a captured message

Forward or reply to a captured message for round-trip flow tests

GET STARTED

Start building with Mailosaur API API

Explore with Jentic

View OpenAPI Document

Use for: Create a Mailosaur server for the staging integration tests, Search for the password-reset email sent to test+abc@mailosaur.io in the last minute, Get the body of message id 9999 to assert on the OTP code, Run spam analysis on the most recent welcome email

Not supported: Does not deliver production email or SMS, manage marketing lists, or run load tests — use for email and SMS testing in CI only.

Use Cases

Patterns agents use Mailosaur API API for, with concrete tasks.

★ End-to-End Signup and OTP Testing

Assert that a signup flow actually delivers the expected email by capturing it on a Mailosaur server in CI. POST /messages/search returns the matching message by recipient and subject filter, GET /messages/{messageId} returns the body, and the test extracts the OTP or confirmation link. Mailosaur eliminates flaky tests that depend on a real inbox.

POST /messages/search with sentTo=test+abc@mailosaur.io and subject containing "Reset", then GET /messages/{messageId} and extract the reset code from the HTML body.

Spam Score Regression

Run spam analysis against every transactional email type on a release candidate to catch regressions in subject lines or content that would push deliverability down. GET /analysis/spam/{messageId} returns SpamAssassin score and per-rule contributions so a CI pipeline can fail the build when the score crosses a threshold.

After the password-reset email is captured, GET /analysis/spam/{messageId} and fail the test if the score exceeds 5.0.

Inbound SMS Test Automation

Capture and assert on inbound SMS flows by provisioning Mailosaur test devices and searching for received messages by phone number or content. This is the right pattern for testing two-factor authentication flows that depend on phone-based one-time passwords without using a real SIM.

Provision a device via POST /devices, trigger the app's SMS OTP flow, then POST /messages/search with the device id and parse the OTP from the latest message.

Round-Trip Reply and Forward Tests

Test workflows that depend on a recipient replying or forwarding a message — for example helpdesk auto-responders or distribution lists — by using POST /messages/{messageId}/reply and POST /messages/{messageId}/forward. The simulated outbound message is delivered through Mailosaur's outbound infrastructure and arrives at the system under test as if a human had pressed reply.

After capturing the helpdesk acknowledgement, POST /messages/{messageId}/reply with a body of "more info please" and assert the helpdesk re-acknowledges within 60 seconds.

Agent-Driven QA Verification

An AI agent that drives a manual-test-replacement workflow can use Mailosaur through Jentic to spin up a test server, run a flow against the system under test, then search and assert on the captured messages. The basic-auth API key lives in the Jentic vault, so the agent has scoped access to test inboxes without exposing credentials.

Create a Mailosaur server, run a signup flow, then poll /messages/search until the welcome email arrives and assert that the activation link is present in the body.

Key Endpoints

23 endpoints — mailosaur is a service for testing email and sms flows in development and ci.

METHOD

PATH

DESCRIPTION

POST

/servers

Create a virtual test mail server

POST

/messages/search

Search inbound messages by criteria

GET

/messages/{messageId}

Retrieve a captured message

GET

/analysis/spam/{messageId}

Run spam analysis on a message

POST

/messages/{messageId}/forward

Forward a captured message

POST

/messages/{messageId}/reply

Reply to a captured message

POST

/devices

Provision an SMS test device

POST

/servers

Create a virtual test mail server

POST

/messages/search

Search inbound messages by criteria

GET

/messages/{messageId}

Retrieve a captured message

GET

/analysis/spam/{messageId}

Run spam analysis on a message

POST

/messages/{messageId}/forward

Forward a captured message

Why though Jentic?

Three things that make agents converge on Jentic-routed access.

Credential isolation

The Mailosaur API key is stored encrypted in the Jentic vault and presented as basic-auth at execution time (key as username, empty password). Agents never read or log the raw key.

Intent-based discovery

Agents search Jentic by intent (e.g., "search mailosaur messages") and Jentic returns POST /messages/search with its input schema, ready to execute against the right server.

Time to first call

Direct integration: half a day to wire up basic auth, message-search polling, and spam-analysis retrieval. Through Jentic: under 30 minutes — search, load, execute.

Related APIs

Alternatives and complements available in the Jentic catalogue.

Complementary

MailerSend API

Transactional email sender that pairs with Mailosaur for end-to-end test flows.

Use MailerSend in production and Mailosaur in CI to assert that the same flow actually delivers the expected message.

Complementary

Mailjet API

Transactional and marketing email provider that can be tested via Mailosaur capture.

Run signup or reset flows through Mailjet in staging and assert on the message via Mailosaur.

Alternative

Twilio Messaging

Real SMS provider — the production equivalent of Mailosaur's test SMS.

Use Twilio Messaging in production for real SMS delivery and Mailosaur devices in CI to test the same flow without sending real messages.

FAQs

Specific to using Mailosaur API API through Jentic.

What authentication does the Mailosaur API use?

Mailosaur uses HTTP Basic authentication via the basicAuth scheme. The username is your Mailosaur API key and the password is left empty (a colon-only password). Through Jentic the API key is stored encrypted in the vault and injected into the Authorization header at execution time.

Can I search messages received in the last minute?

Yes. POST /messages/search accepts criteria such as sentTo, sentFrom, subject, and body, plus a server id. It returns the most recent matching messages, which is the standard pattern for e2e tests that wait for a freshly sent email after triggering a flow.

What are the rate limits for the Mailosaur API?

Mailosaur uses a credit-based usage model rather than a per-second rate limit. GET /usage/limits returns your current limits and GET /usage/transactions returns recent consumption. The OpenAPI spec does not declare a per-second cap.

How do I run a signup-email test through Jentic?

Search Jentic for "search mailosaur messages" to load POST /messages/search, then execute with the recipient address that your signup test used. Follow up with GET /messages/{messageId} to extract the body and assert on the activation link or OTP.

Is the Mailosaur API free?

Mailosaur offers a free trial for evaluation; production use requires a paid plan whose monthly credit allowance is reported via /usage/limits. Pricing tiers are listed at https://mailosaur.com/pricing.

Can I test inbound SMS as well as email?

Yes. POST /devices provisions an SMS-capable test device, and inbound SMS messages are captured the same way as emails — searchable through POST /messages/search with the device id and inspectable through GET /messages/{messageId}.