How to Build a Shared Customer Inbox Across Slack, Gmail, and Microsoft Team

March 23, 2026

A shared customer inbox is a feature inside a SaaS product that aggregates conversations from messaging and email platforms into a single interface, allowing teams to read, reply, and manage customer communication in one place.

To build this, your product needs to retrieve messages from platforms like Slack, Gmail, and Microsoft Teams, group them into threads, and allow users to respond without switching tools.

The challenge is that each platform exposes different APIs, message formats, and threading models. Unified provides a consistent Messaging API that lets your product retrieve and send messages across these platforms using a single interface.

Why SaaS Products Build Shared Inbox Features

Many B2B SaaS products provide shared inbox functionality for their customers.

Examples include:

• Customer support platforms
• Sales communication tools
• Customer success platforms
• Helpdesk products
• AI support assistants

These products allow teams to manage communication across channels in one place.

Typical use cases include:

• Support inboxes for handling customer requests
• Sales inboxes for managing outbound and inbound communication
• Customer success inboxes for account management
• AI-assisted inboxes for automated replies and summaries

Common Shared Inbox Use Cases

Shared inbox features typically support several workflows.

Unified conversation view

Display messages from Slack, Gmail, and Teams in a single interface.

Threaded conversations

Group related messages into conversation threads.

Multi-channel replies

Allow users to respond to messages across platforms.

Team collaboration

Let multiple users participate in conversations.

Automated responses

Use AI to suggest or generate replies.

Unified Messaging Category

The Messaging API normalizes communication across multiple platforms.

This allows your product to retrieve and send messages across providers using the same API structure.

Unified Message Object and Key Fields

The message object represents a single communication event.

Important fields include:

These fields allow your product to display conversations consistently across platforms.

Connecting Customer Messaging Platforms

Customers connect their messaging platforms using Unified Connect.

Typical flow:

1. Your application launches the authorization flow.
2. The user selects integrations such as Slack, Gmail, or Microsoft Teams.
3. The user authorizes access.
4. Unified returns a connection_id.

Your application stores:

user_id → connection_id

All API requests reference this identifier.

Retrieving Messages and Threads

Messages are retrieved using:

GET /messaging/{connection_id}/message
GET /messaging/{connection_id}/channel

Thread model

Unified does not provide a separate thread object. Threads are reconstructed using message metadata.

Parent-based threading

• Each message includes a parent_id
• Messages without a parent_id are root messages
• Replies reference their parent message

Thread grouping

You can group messages by:

• root message (no parent_id)
• or message_thread_identifier (if available)

Fetching full thread history

Two approaches:

Filter by parent

GET /messaging/{connection_id}/message?parent_id={message_id}

Returns direct replies.

Expand full thread

Use expand=true when listing messages to return all nested replies in a single request.

This allows your product to reconstruct complete conversations.

Sending and Replying to Messages

Unified uses a single endpoint to send new messages and replies.

POST /messaging/{connection_id}/message

Sending a new message

Provide:

• message content (message)
• recipients (channels or email fields)

Replying to a thread

Set:

parent_id = existing_message_id

This ensures the message appears in the correct thread.

Writable fields

Updating messages

PUT /messaging/{connection_id}/message/{id}

Used to edit messages (supported in platforms like Slack).

Building a Shared Inbox Interface

A shared inbox typically combines messages into a single UI.

Example structure:

Applications typically:

1. Retrieve messages across platforms
2. Group them into threads
3. Sort by created_at
4. Display participants using author_member and recipient fields
5. Allow replies using the messaging API

Because Unified normalizes message objects, this logic works across all supported providers.

Keeping Inbox Data Updated

Unified provides webhook events for messaging updates.

Common events include:

• message.created
• message.updated
• message.deleted

Additional interaction events include:

• reactions
• mentions
• button clicks

These events allow your inbox to:

• update in real time
• show unread messages
• trigger notifications
• power AI workflows

Supported Platforms

Unified supports multiple messaging integrations.

Examples include:

• Slack
• Gmail
• Microsoft Teams
• Outlook
• Intercom
• Zendesk

This allows your product to support communication across multiple channels.

Why This Matters

Building a shared inbox requires integrating multiple messaging platforms and handling different APIs, threading models, and message formats.

Unified simplifies this by providing:

• normalized message objects across platforms
• a single endpoint for sending and replying to messages
• consistent thread reconstruction using parent_id
• real-time updates via webhooks

This allows product teams to focus on building inbox features instead of managing integration complexity.

Start building shared inbox features across Slack, Gmail, Microsoft Teams, and other messaging platforms today.

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