Outlook Semantic MCP – Features

This page describes user-facing features of the Outlook Semantic MCP Server: what is supported, what is not, and any setup required. For per-tool input/output reference, see Tools. For environment variables and deployment configuration, see Configuration.

Deployment modes

The MCP server operates in two modes controlled by the MCP_BACKEND environment variable. Several features behave differently depending on which mode is active:

Where a feature works the same in both modes, this page says so once. Where behaviour differs, Mode A and Mode B are called out separately.

Email Search

Mode A (microsoft_graph_and_unique_api)

• search_emails runs semantic search against the Unique knowledge base and a KQL keyword search against Microsoft Graph simultaneously, then merges and deduplicates results.

• Folder filtering is supported: pass folder IDs (from list_mailboxes_and_directories) or well-known folder names (e.g. Inbox) to narrow results to a specific folder.

• A syncWarning is returned while the initial full sync is still in progress — results may be incomplete until it finishes.

Mode B (microsoft_graph)

• search_emails queries Microsoft Graph directly using KQL keyword search only. No knowledge base interaction occurs.

• Folder filtering is supported via the directories field on each msGraphKeywordSearchQueries entry. Pass a well-known folder name (e.g. Inbox) or a folder ID from list_mailboxes_and_directories. This works for the user's own mailbox and for fully delegated mailboxes (Full Access).

• Search is not supported for mailboxes where the user only has folder-level (partial) access — Microsoft Graph requires full mailbox access for $search queries.

What's not supported (both modes)

• Calendar, task, or file data — only mail is in scope.

Draft Creation

Available in both modes. Behaviour is identical.

What's supported

• Create draft emails in the signed-in user's Drafts folder via create_draft_email, with subject, body, recipients (To, CC, BCC), and attachments.

• The draft is not sent automatically — the tool response includes a webLink for the user to open and send from Outlook.

• Attachments can be provided as base64-encoded data URIs or Unique content URIs (cluster-local mode only).

What's not supported

• Sending email directly from the MCP — drafts must be sent manually by the user.

• Creating drafts in another user's mailbox (delegated or otherwise).

Contact Resolution

Available in both modes. Behaviour is identical.

What's supported

• Look up contacts in the signed-in user's Microsoft contacts directory via lookup_contacts.

• Returns display names and email addresses for address resolution.

What's not supported

• Organisation-wide directory queries beyond what the People.Read scope exposes. If a contact is not in the signed-in user's personal contacts or the People API result set, it will not appear.

Mailbox & Folder Listing

Mode A (microsoft_graph_and_unique_api)

• List own mailboxes and their full folder tree via list_mailboxes_and_directories.

• When DELEGATED_ACCESS_SCAN is enabled, delegated mailboxes also appear alongside the user's own (marked with isOwn: false).

• Folder IDs returned by this tool can be passed to search_emails to narrow results to a specific folder.

Mode B (microsoft_graph)

• list_mailboxes_and_directories is available and returns the user's own folder tree plus any fully delegated mailboxes. Folder IDs returned here can be passed to the directories field of msGraphKeywordSearchQueries in search_emails to narrow results to a specific folder.

What's not supported

• Searching in mailboxes where the user only has folder-level (partial) access in Mode B — Microsoft Graph does not support $search against such mailboxes.

Delegated Access

Delegated access lets a user search another user's mailbox when Microsoft Exchange has granted them access. The MCP server detects these relationships automatically via background scans controlled by DELEGATED_ACCESS_SCAN — no per-user configuration is needed beyond enabling that setting. Detection only works when both the owner and the delegate have connected the MCP.

What's supported

Three delegation configurations are supported:

1. Exchange admin grants Full Access (Read & Manage)

   • An Exchange administrator grants a user Full Access to another user's mailbox via the Exchange admin center or PowerShell.

2. User shares specific folders via Outlook desktop

   • A user shares individual folders with another user directly from Outlook desktop, without Exchange admin involvement.

3. Shared inbox configured as a normal mailbox

   • A Microsoft 365 shared mailbox configured with a sign-in-eligible password. Every user who needs access must have Full Access delegation granted.

What's not supported

• Microsoft 365 shared mailboxes not configured as a normal mailbox — shared mailboxes that have not been configured with a sign-in-eligible password and an MCP login are not detected or ingested.
• Application-permission based access — the MCP uses delegated permissions only (acting on behalf of a signed-in user).

Setup

1. Exchange admin grants Full Access

Option A — Exchange admin center (GUI)

1. Open the Microsoft 365 admin center and navigate to Exchange admin center.
2. Go to Recipients → Mailboxes and select the target mailbox.
3. Open the Delegation tab.
4. Under Full Access, click Edit and add the delegate user.

Option B — PowerShell

Add-MailboxPermission `
  -Identity "owner@example.com" `
  -User "delegate@example.com" `
  -AccessRights FullAccess `
  -InheritanceType All

2. User shares specific folders (no admin needed)

Requires DELEGATED_ACCESS_SCAN=granular_access and Mode A.

3. Shared inbox configured as a normal inbox

1. In the Microsoft 365 admin center, open the shared mailbox and enable sign-in by assigning it a password.
2. Grant Full Access to every user who needs delegated search access.
3. Connect the MCP using the shared-inbox account itself so its emails are ingested into the Unique knowledge base.

Behavior

For a detailed description of how delegated access works at runtime, see the existing FAQ entries:

Quick reference:

Known Limitations

Search does not work for mailboxes where a colleague shared folders without granting Full Access (Mode B only)

Symptom: When a colleague has shared one or more folders with you (but has not granted you Full Access to their entire mailbox), search_emails in Mode B returns no results from that mailbox.