Inbound

Inbound Email Processing

Receive, parse, and route incoming emails with webhooks, forwarding, or database storage. Per-address routing with wildcard support.

How it works

1

Email arrives

Incoming email is received and stored securely with no size limit.

2

Parsed & queued

The email is parsed into text/HTML with attachment metadata, and queued for processing.

3

Route by address

Each recipient address can have its own routing rule. Use wildcards to catch all addresses on a domain.

4

Action executed

The email is delivered to your webhook, forwarded to another address, stored in your database, or dropped.

Capabilities

Webhook Routing

POST parsed email data to your endpoint with HMAC-SHA256 signature verification. Includes headers, text, HTML, and attachment metadata.

Email Forwarding

Forward incoming emails to any address with full attachment support. Attachments are included in the forwarded message automatically.

Database Storage

Store parsed emails directly in your Transmit database. Search and retrieve via API or dashboard.

Wildcard Routing

Set up catch-all rules with wildcard patterns. Route support@, billing@, and *@ to different destinations.

Webhook Payload

json
{
  "from": "customer@example.com",
  "to": ["support@yourapp.com"],
  "subject": "Help with my order",
  "text": "I need help with order #1234...",
  "html": "<p>I need help with order #1234...</p>",
  "headers": {
    "message-id": "<abc123@example.com>",
    "date": "Thu, 06 Feb 2025 10:30:00 +0000"
  },
  "attachments": [
    {
      "filename": "screenshot.png",
      "mimeType": "image/png",
      "size": 45230
    }
  ]
}

Related features

SMTP

SMTP Relay

Drop-in SMTP server for legacy apps. Send through Transmit without changing your application code. Just update your SMTP credentials.

Webhooks

Email Webhooks

Real-time notifications for email events. Get instant delivery, bounce, open, click, and complaint data pushed to your endpoint.

Frequently Asked Questions

What is an inbound email API?
An inbound email API lets your application receive and process incoming emails programmatically. Instead of checking a mailbox, emails are parsed and delivered to your code via webhooks, stored in a database, or forwarded to another address.
How are attachments handled?
Attachments are stored securely when the email arrives. Webhook payloads include attachment metadata (filename, size, MIME type) but not the binary content, keeping payloads small. For forwarding, attachments are included in the forwarded message automatically.
What actions are available for inbound emails?
Four actions: webhook (POST to your URL), forward (send to another email address with attachments), store (save to database), and drop (discard the email). Each recipient address can have a different action.
How do I verify webhook signatures?
Every webhook request includes an HMAC-SHA256 signature in the X-Signature header. Compute the HMAC of the raw request body using your webhook secret and compare it to the header value to verify authenticity.
What's the size limit for inbound emails?
There is no practical size limit for receiving emails. Our pipeline bypasses the size restrictions other providers impose. Attachments of any size are supported.
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