M365 Copilot — Copilot in Outlook

At a glance

What Copilot reads automatically
The open email and its thread history.
No @ reference needed inside Outlook.

What it cannot access
Emails in other people's inboxes.
Shared mailboxes require separate configuration.

The highest-return feature
Thread summarisation — collapses a 40-reply thread
to three sentences before you open a single message.

Capability	What it does	For
Thread summary	Collapses long email threads to key points, decisions, and open items	Anyone managing high email volume
Draft with Copilot	Generates a reply or new email from a prompt — tone, length, and structure specified	Sales · PM · EA · Manager
Coaching	Reviews a draft for tone, clarity, and length before you send	Anyone sending high-stakes external emails
Meeting prep brief	Summarises email context with a contact before a call	Sales · Manager · Executive
Suggested replies	One-click short response options at the bottom of an email	High-volume inboxes · mobile users
Action mode	Copilot Chat operates on your inbox — drafts replies, creates rules, triages, and categorises via natural language	Frontier · M365 Copilot licence · Anthropic subprocessor · Not EU
Voice inbox triage	Manage your inbox hands-free on mobile — summarise, flag, pin, archive, and mark as read through natural conversation	M365 Copilot licence · Outlook mobile (iOS/Android)
Open email in chat	View a referenced email directly inside the Copilot pane without leaving the conversation	M365 Copilot licence · No admin action needed

Core capabilities — what each one does

Thread summarisation

Select any email thread and click Summarise. Copilot reads the full thread — including replies buried in the chain — and returns key points, decisions made, and open items. Works on threads of any length.

Summarise this thread and list any unresolved questions."
What commitments were made in this thread, and by whom?"
Give me a 3-sentence brief on this conversation for a colleague who wasn't copied."

Draft with Copilot

In a reply or new message, click the Copilot icon in the compose window. Describe what you want to say — Copilot writes the full draft. Adjust length (short/medium/long) and tone (formal/casual/direct/informational) before generating.

Draft a follow-up to this thread acknowledging the delay and proposing Thursday for a call."
Write a brief reply thanking the team and confirming we'll proceed with option 2."
Draft a cold outreach to a procurement contact at a large engineering firm."

Coaching

After drafting an email, click Coaching by Copilot. Copilot reviews the text across four dimensions — tone, reader sentiment, clarity, and conciseness — and gives specific suggestions before you send.

Is this email too long? What would you cut?"
How might this read to someone who didn't expect this news?"
Flag anything that sounds defensive or ambiguous."

Meeting prep brief

Open a calendar event and click Prepare for this meeting. Copilot summarises recent email and Teams communication with the meeting participants — commitments made, topics discussed, items likely to come up.

What open items from this thread should I address in today's call?"
What has [contact name] raised in their last 3 emails to me?"
Summarise the context of this relationship in under 100 words."

Open email in Copilot Chat

When Copilot references an email in Copilot Chat, click to open that email directly inside the Copilot pane. The email appears beside the conversation — no inbox context switch required. Available GA worldwide mid–late May 2026. Enabled by default. No admin action or Frontier enrolment needed.

Use after asking Copilot to find a specific email — open it in-pane to verify the source without losing your chat."
Combine with thread summary: ask for a summary, then open the original alongside the answer."

Coaching — what it checks

Four dimensions Copilot scores your draft on

Tone

Is the register appropriate for the recipient? Copilot flags language that reads as overly formal, too casual, or unintentionally abrupt.

Reader sentiment

How might the recipient feel reading this? Copilot flags language that may land as negative, dismissive, or presumptuous — even when not intended.

Clarity

Is the key ask or point clear? Copilot identifies buried requests, ambiguous phrasing, and sentences that require re-reading.

Conciseness

Is every sentence earning its place? Copilot flags preamble, filler phrases, and repeated ideas — then suggests specific cuts.

Before and after — the gap in practice

Same inbox · same email · with and without Copilot

Catching up on a 30-reply thread

Without Copilot

Open and read 30 emails to understand the current status.

5–10 minutes. Easy to miss a buried decision or a commitment made in a mid-thread reply.

With Copilot

Click Summarise. Read 3 sentences: what was decided, what's open, who owes what.

30 seconds. Open individual emails only for messages that need a response.

Drafting a difficult reply

Without Copilot

Write from scratch. Re-read three times. Still not sure if the tone is right.

10–15 minutes for a 4-sentence reply. Risk of sending something that reads poorly.

With Copilot

Describe the situation in one line. Copilot drafts. Coaching flags the one sentence that sounds defensive. Edit and send.

3 minutes. Higher-quality output than the unassisted draft.

Preparing for a client call in the next 15 minutes

Without Copilot

Scan the last 5 emails manually. Hope you catch the open item the client mentioned twice.

Likely to miss something. Full context takes longer than 15 minutes to reconstruct.

With Copilot

Open the calendar event → Prepare for this meeting. Read the brief. Know the open items before the call starts.

Complete pre-call context in 90 seconds. Nothing from the last 30 days is missed.

Use cases by role

High-volume inbox management

Manager · Team Lead · EA · anyone with 100+ emails/day

Inbox

When to use

After returning from leave or a full-day meeting block
At the start of the day to triage before acting
Before a leadership meeting to confirm nothing is open

Prompts (in Copilot Chat, inbox context)

Summarise my unread emails from today. List sender, subject, and whether any action is required."
Are there any emails flagged or marked urgent that I haven't replied to?"
Which threads from this week have an open question directed at me?"

Thread summarisation works inside the open email. For cross-inbox triage, use Copilot Chat (paid, Work mode) with the prompts above.

Sales and client communication

Sales · Account Manager · Business Development

Sales

When to use

Before any discovery or renewal call with a client
Drafting a follow-up after a meeting where commitments were made
Catching up on a thread you were added to mid-way through

Prompts

Summarise this thread. What has the client asked for that I haven't confirmed yet?"
Draft a follow-up email confirming the three items discussed in today's call. Tone: professional, brief."
What objections has this contact raised across our recent email exchange?"

Pair with Scheduled Prompts for automated follow-up gap detection every Wednesday morning. See the Scheduled Prompts guide.

Formal and sensitive communication

Legal · Compliance · HR · Executive · anyone sending high-stakes external emails

High stakes

When to use

Any external email where tone could be misread
Difficult internal messages (performance, escalation, dispute)
Emails that will be forwarded or referenced later

Prompts (via Coaching)

How would this read to someone who wasn't expecting this news?"
Is any part of this email ambiguous about what I'm committing to?"
Does this email make any claim I cannot fully support?"

Use Coaching before sending, not after. Once sent, Copilot cannot retrieve or unsend the email.

New capabilities — rolling out 2026

Action mode · Voice triage · Open email in chat

Copilot Action Mode — inbox operations via natural language

Anyone with Frontier enrolment and M365 Copilot licence · Not available in EU

Frontier

What it can do

Draft and send replies directly from Copilot Chat
Create and manage inbox rules via natural language
Triage and archive emails on request
Identify non-responders after 24 hours
Generate post-vacation inbox summaries
Auto-apply colour categories to high-priority messages

Example prompts (action mode active)

Archive everything in my inbox older than 30 days that isn't flagged."
Create a rule to move all emails from @vendor.com to the Vendors folder."
Which emails from this week have had no reply from the other side for more than 24 hours?"
Give me a summary of everything that came in while I was on leave."
Tag all emails from my manager as high priority."

Requirements — all three must be active: (1) M365 Copilot licence · (2) Frontier programme enrolment · (3) Anthropic subprocessor enabled by your admin (admin.microsoft.com → Copilot → Settings). In EU/EFTA/UK tenants, Anthropic is off by default — admin opt-in required. Government/Sovereign cloud: Anthropic fully excluded, action mode unavailable. Not available to EU users regardless of subprocessor setting. Supported clients: Outlook on the Web, Classic Outlook for Windows, Outlook for Windows, iOS, Android. Toggle back to chat-only mode via the "default mode" dropdown above the Copilot prompt box. Action mode runs on Claude (Anthropic). Source: MC1293485, rolled out Apr 27–28, 2026.

Voice inbox triage — manage your inbox hands-free on mobile

Anyone on Outlook mobile · iOS and Android · M365 Copilot licence

GA · Mobile

Available voice actions

Summarise recent unread emails
Flag, pin, archive, mark as read
Ask follow-up questions mid-conversation
Read a full thread from start to finish
Interrupt or redirect Copilot at any point

Example voice prompts

Summarise my last five unread emails."
Flag that one and archive the rest."
Read me the full thread from [sender name]."
Mark all of those as read."
Any emails from my manager today?"

Requirements: M365 Copilot licence · Latest version of Outlook mobile (iOS or Android). Open Copilot in the Outlook app, then tap Voice. No Frontier enrolment required. No EU exclusion. No admin configuration needed. Not available via voice: creating inbox rules, drafting replies, accessing custom folder contents. GA Worldwide late April–late May 2026. Source: MC1187805.

What Copilot in Outlook cannot do

Access other people's inboxes or shared mailboxes

Copilot reads your own inbox and sent items. Shared mailboxes require delegated access to be configured by an admin before Copilot can assist with them.

Fix: Contact your Microsoft admin or check your organisation's licence portal to enable Copilot for shared mailboxes if your role requires it.

Read email attachments automatically

Copilot reads the email body only. Attachments — PDFs, Word docs, spreadsheets — are not included in thread summaries or draft context unless you reference them separately.

Fix: Upload the attachment to OneDrive and reference it with @filename in Copilot Chat for attachment-based queries.

Summarise across more than ~10 emails in a thread

Copilot applies a per-query email cap. On very long threads, it summarises the most recent and most relevant messages — earlier context may be omitted without warning.

Fix: For very long threads, ask Copilot to summarise in sections: "Summarise the last 5 replies" then "Summarise the earlier discussion in this thread."

Send, move, or delete email on your behalf (standard Copilot)

Standard Copilot in Outlook drafts and coaches. It does not perform actions on your mailbox. All sends and moves are initiated by you.

Note: Automated email actions at scale require a Power Automate flow or a Copilot Studio agent. Action mode (Frontier) can perform triage and archiving, but requires Frontier enrolment and Anthropic subprocessor enabled.

Action mode: click unsubscribe links or exclude weekends from silence detection

Even in action mode, Copilot cannot interact with unsubscribe links or reliably exclude weekends and holidays when identifying non-responders. Silence detection counts calendar days, not business days.

Fix: For unsubscribe management, use the manual Unsubscribe button in Outlook. For non-responder detection, factor in weekend gaps when reviewing Copilot's output.

Action mode: not available for EU users or without Anthropic subprocessor enabled

Action mode requires the Anthropic subprocessor to be enabled by your admin. In EU/EFTA/UK tenants it is off by default. In Government/Sovereign cloud it is fully excluded. EU users cannot access action mode regardless of admin settings.

Fix: EU users and Government/Sovereign cloud tenants should use standard Copilot Chat prompts for triage, or a Copilot Studio agent with action connectors as an alternative. Non-EU admins enable Anthropic at admin.microsoft.com → Copilot → Settings.

Voice triage: draft replies, create rules, or access custom folders

Voice inbox triage on mobile supports read and triage actions only. You cannot draft or send replies, create inbox rules, or access custom folder contents through the voice interface.

Note: For drafting and rule creation on mobile, switch from Voice to the standard Copilot Chat text interface within the Outlook app.

Rules to follow

1Run Coaching before sending any high-stakes email. It takes 10 seconds and catches the tone and clarity issues that read poorly only after you've sent.
2Use Draft with Copilot for a first draft, not a final one. Copilot's draft gives you a starting point. Read it, adjust the specifics, then send. Do not forward a Copilot draft without reading it.
3Thread summarisation does not replace reading critical emails. Use it to triage what to read, not to avoid reading entirely. For any email requiring action or sign-off, open the source.
4Meeting prep brief is most useful when run 15–30 minutes before a call. Running it the night before gives less actionable context — communications from the morning may have changed the situation.
5Copilot reads your sent items too. Thread summaries include your own replies. This means it captures commitments you made — not just ones others made to you.