Postalserver Postal API

Name: Postal API
Brand: Postal API
Availability: InStock

✓ Official Vendor SpecCommunicationsEmail DeliveryapiKey4 EndpointsREST

For Agents

Send transactional emails with attachments and custom headers, submit raw RFC 2822 messages, and track delivery status through a self-hosted mail server.

Install Jentic One Beta

Connect the Postal API to your agent

Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the Postal 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.

Step 1: Jentic One Host machine

# On the machine that will host your Jentic One instance:
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh

Step 2: Agent machine

# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh
jentic register       # connects your agent to your Jentic One instance

Jentic 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 Postal API.

Send structured emails with multiple recipients, CC, BCC, and file attachments

Submit pre-crafted RFC 2822 messages for full control over email formatting

Retrieve sent message details including status, timestamps, and routing metadata

GET STARTED

Start building with Postal API

Explore with Jentic

View OpenAPI Document

Use Cases

Patterns agents use Postal API for, with concrete tasks.

★ Transactional Email Delivery

Send order confirmations, password resets, and notification emails through a self-hosted mail server. The Postal API accepts structured parameters including recipient lists, HTML and plain text bodies, custom headers, and base64-encoded attachments. Messages are tagged for tracking and return a unique message ID for delivery verification.

Send an email via the /send/message endpoint to user@example.com with subject 'Order Confirmed', an HTML body, and tag 'order-confirmation'

Email Delivery Monitoring

Track whether sent emails reached their destination by querying the deliveries endpoint for a specific message. Postal returns delivery attempt details including SMTP response codes, timestamps, and failure reasons, enabling automated alerting when critical emails bounce or get deferred.

Retrieve the delivery status for message ID 12345 using the /messages/deliveries endpoint and check whether delivery succeeded

Raw Message Submission for Migration

Submit pre-formatted RFC 2822 email messages for scenarios where the full message is already constructed, such as email migration tools, mailing list software, or relay configurations. The raw endpoint accepts base64-encoded message data with explicit MAIL FROM and RCPT TO parameters.

Send a raw RFC 2822 message via the /send/raw endpoint with mail_from set to sender@domain.com and rcpt_to containing the recipient address

AI Agent Email Sending via Jentic

AI agents use Jentic to discover Postal operations by intent, such as 'send a transactional email'. Jentic returns the sendMessage operation schema with required fields (to, from) and optional fields (subject, html_body, attachments), then handles X-Server-API-Key injection so the agent sends emails without managing server credentials.

Search Jentic for 'send a transactional email', load the sendMessage schema, and execute an email delivery to notify@example.com with a plain text body

Key Endpoints

4 endpoints — postal is an open-source mail delivery platform providing an http api for sending transactional and operational emails.

METHOD

PATH

DESCRIPTION

POST

/send/message

Send a structured email with recipients, body, and attachments

POST

/send/raw

Send a raw RFC 2822 formatted message

POST

/messages/message

Retrieve details of a sent message by ID

POST

/messages/deliveries

Get delivery attempts for a specific message

POST

/send/message

Send a structured email with recipients, body, and attachments

POST

/send/raw

Send a raw RFC 2822 formatted message

POST

/messages/message

Retrieve details of a sent message by ID

POST

/messages/deliveries

Get delivery attempts for a specific message

Why Jentic?

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

Credential isolation

Postal X-Server-API-Key credentials are stored encrypted in the Jentic vault. Agents receive scoped access so that mail server keys never appear in agent context or logs.

Intent-based discovery

Agents search by intent (e.g., 'send a transactional email' or 'check delivery status') and Jentic returns the matching Postal operation with its input schema, so the agent calls the right endpoint without browsing self-hosted documentation.

Time to first call

Direct Postal integration: 1-2 days for server URL configuration, key management, and delivery tracking setup. Through Jentic: under 30 minutes — search, load schema, execute.

FAQs

Specific to using Postal API through Jentic.

What authentication does the Postal API use?

The Postal API authenticates using an X-Server-API-Key header. This key is created through the Postal web interface for each mail server. Through Jentic, the server API key is stored encrypted in the vault and injected into request headers automatically.

Can I send emails with attachments using the Postal API?

Yes. The /send/message endpoint accepts an attachments array where each attachment includes a name, content_type, and base64-encoded data field. You can attach multiple files to a single message.

What are the rate limits for the Postal API?

Since Postal is self-hosted, rate limits depend on your server configuration and infrastructure capacity. There are no externally imposed API rate limits. Throughput is determined by your mail server's processing capacity and outbound IP reputation.

How do I check email delivery status through the Postal API with Jentic?

Install the SDK with pip install jentic, then search for 'check email delivery status'. Jentic returns the getMessageDeliveries operation schema requiring a message id parameter. Execute the call with your message ID to receive delivery attempt details including SMTP response codes.

What is the difference between /send/message and /send/raw?

The /send/message endpoint accepts structured parameters (to, from, subject, html_body, plain_body, attachments) and Postal constructs the email. The /send/raw endpoint accepts a pre-built RFC 2822 message as base64-encoded data, giving full control over headers and formatting for migration or relay use cases.

Is the Postal API free to use?

Yes. Postal is open-source software that you host on your own infrastructure. There are no per-email fees or API usage charges. Costs are limited to your server hosting and any DNS or IP reputation services you choose to use.

Postalserver Postal API

Connect the Postal API to your agent

Capabilities

Start building with Postal API

Use Cases

Key Endpoints

Why Jentic?

Related APIs

FAQs