Custom channels

Build custom channels to bring any messaging platform into Missive.

Build your own integrations with Missive using custom channels. Receive messages from any source via API and optionally send outgoing messages through webhooks.

Custom channels are for developers who want to integrate proprietary systems, niche platforms, or internal tools with Missive.

Use cases

• Internal ticketing systems: Route support tickets to Missive

• CRM integrations: Sync customer communications

• Proprietary platforms: Connect platforms without native Missive support

• IoT and monitoring: Receive alerts as conversations

• Custom chat widgets: Build your own chat solution

Message types

When creating a custom channel, choose a message type. This cannot be changed after creation.

Type	Description	Use case
Text	Basic text with emojis, attachments, bubble colors	Chat-like messages, alerts
HTML	Rich-text HTML content with attachments	Formatted notifications, reports
Email	Subject, From/To/Cc/Bcc, HTML body	Email-like messages (receive only)

How to create

1

Open account settings

Go to Settings > Accounts and click Add account.

To open Settings, click your avatar at the top of the sidebar, then Settings (or press ⌘,).

2

Select Custom

Click the Others tab, then select Custom.

3

Choose sharing options

Select if this is a personal or shared account.

4

Configure basic settings

Enter:

• Username: Display name for this channel in Missive

• Message type: Text, HTML, or Email (cannot be changed later)

5

Configure message settings

Set up outgoing message options:

• Allow sending new messages: Enable to compose new messages

• Allow replying: Enable to reply to incoming messages

• Allow editing recipients: Let users change recipient fields

Configure recipient fields:

• Allow recipient ID: Custom identifier for routing

• Allow recipient name: Display name for recipients

• Allow recipient username: Username or handle

6

Set up aliases (optional)

Add sender identities your team can use when sending:

• ID: Internal identifier

• Name: Display name

• Username: Handle or email-like address

7

Configure webhook (if sending enabled)

If outgoing messages are enabled:

• Outgoing webhook URL: Endpoint that receives message payloads

• Signature secret: HMAC SHA256 key for request validation

The webhook receives a POST request when messages are sent from Missive.

8

Create the channel

Click Connect to create your custom channel. Note the channel ID for API integration.

Receiving messages

Send messages to your custom channel via the Missive REST API.

POST /v1/messages

Include the channel_id in your request. See the Custom Channels API documentation for details.

Sending messages (webhook)

When users send or reply from Missive, your webhook receives a POST request with:

• Message content

• Recipient information

• Sender alias details

• Conversation context

Webhook validation

If you set a signature secret, validate requests using HMAC SHA256:

1. Get the X-Missive-Signature header

2. Compute HMAC SHA256 of the raw request body using your secret

3. Compare signatures using constant-time comparison

Customization

Bubble colors (Text type)

Set custom colors for incoming message bubbles.

Aliases

Define multiple sender identities for your team.

Recipient fields

Control which recipient fields users can set.

Developer documentation

For complete API details, see:

• Custom Channels API

• REST API reference

• Webhooks