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

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."

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.

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

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 require a Power Automate flow or a Copilot Studio agent with action connectors — not Outlook Copilot.

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.