Copilot works from the access of whoever is typing. Here's how an executive and an EA or chief of staff can share it without losing track of who saw what.
The useful question for an executive isn’t which Copilot feature to use, but who prompts on whose access, who checks, and who sends. Microsoft documents that Copilot only surfaces what the person prompting can already see, that Copilot Chat now works in shared and delegated mailboxes to read and draft, and that sending and scheduling there aren’t supported yet. Write those limits into a one-page agreement between you and your EA or chief of staff, give each job a level of delegation and a named checker, and review it with Use, Persistence and Impact rather than prompt counts.
Say you’re the CEO of a mid-sized company, and your executive assistant has started leaving a one-page brief in your inbox at 7:40 on Monday mornings. It’s good. It lists what needs your decision, who’s waiting on you, and three calendar collisions you’d otherwise have found out about on Wednesday. On the second Monday you ask about line three, a vendor renewal you didn’t know was live. She says Copilot found it in a long thread, and she can’t say which one.
You believe her. But you also realize you can’t answer three things. Whose access did Copilot use to find that thread? What else could it see that didn’t make it into the brief? And who would have caught it if line three had been wrong?
Those three questions are this article. Copilot works from whatever the person typing is allowed to see, so an executive who works through an EA or a chief of staff has two Copilots, two sets of access and two prompt histories, usually with no agreement about any of them. What helps is a short working agreement: who prompts, on whose access, who checks, and who’s allowed to send.
If you want to know what Copilot does for a CEO versus a CFO or a CHRO, our role-by-role guide for executives covers it, and the personal AI playbook covers your own habits when you’re working solo. This piece is about the pair. It also follows our working rule for Copilot, which is a judgment rather than a Microsoft claim: it earns its place when it reads, compares, finds, challenges and verifies work that already exists, so that’s where the delegation below points it.
Product facts come from Microsoft’s own support and Learn pages, read in late September 2026, and I’ve flagged the places where two of them disagree. The operating advice is our judgment, and it’s labelled that way.
Everything else here hangs on one sentence from Microsoft: Copilot only surfaces organizational data to which the person prompting has at least view permission.[4] It doesn’t matter whose meeting, whose mailbox or whose deck the question is about. It matters who’s signed in.
That holds when an assistant works inside your mailbox. Microsoft’s support page for Copilot Chat in shared and delegated mailboxes says it respects the permissions your assistant already has, doesn’t elevate access, and saves the conversation history to your assistant’s primary account rather than yours. It can summarize and draft, and it can summarize delegate calendars, so “What meetings do I have today?” returns the delegate mailbox’s meetings. It can’t yet triage mail, send on your behalf, or schedule and update meetings.[1] In practice your EA’s Copilot reads and drafts, and your EA still sends and books.
The rules have moved recently, so it’s worth checking your own sources. Microsoft’s requirements page previously excluded shared and delegate mailboxes, as earlier write-ups quoted it. The version updated on 24 September 2026 says Copilot supports them, and that group mailboxes aren’t supported.[3] An older support page from February 2026 said Copilot couldn’t help if you only have shared folder permissions in a delegate mailbox,[2] while the current page says folder-level permissions are supported alongside Full Access. Older write-ups, ours included, may still carry the earlier wording, so test it in your assistant’s own setup before you build a routine on it.
Licensing is the other thing to confirm. The February page says you must have a Microsoft Copilot licence to read or act on items in shared and delegate mailboxes. It’s written about the person doing the reading, and nothing I found says the mailbox owner needs a seat too, so ask your admin to confirm it for your tenant.
| Whose Copilot | Runs on whose access | Where its prompt history sits | Check first (our judgment) |
|---|---|---|---|
| Your own | Yours | Your account | Whether your own file access is wider than your job now needs |
| Your EA, in your delegated mailbox | Your EA’s permissions on your mailbox: Full Access or folder level | Your EA’s primary account, not yours | That your EA holds a Microsoft Copilot licence, and which folders they were actually given |
| Your EA, in their own files and mail | Your EA’s | Your EA’s account | Old shares and site memberships your EA picked up over the years |
| Your chief of staff | Their own, plus a mailbox only if you’ve delegated it | Their account | Whether they can see the strategy and board files the brief assumes they can |
Built from Microsoft’s delegated-mailbox and privacy documentation. The last column is a suggested first check, not a Microsoft statement.
A Copilot answer describes what the person typing can see, not everything that exists.
That’s why an assistant’s brief can look complete and still miss something. It isn’t a flaw in the prompt, just a boundary. An EA who has run your calendar for years may be able to see more than you’d guess, and a chief of staff may see far less of your mailbox than you assume.
With the access question on the table, the next question is what to hand over. The tempting version is “let her use Copilot on my stuff”. The workable version names three levels and puts one person’s name against each.
| Level | What the EA’s Copilot does | Example | Who signs off |
|---|---|---|---|
| 1. Prepare | Reads, finds and compares. Nothing leaves the EA’s screen. | The Monday brief; every email around the vendor renewal, with senders and dates; a calendar collision scan | The EA, who opens the source before it goes into the brief |
| 2. Draft | Produces draft replies and notes for a person to edit. | A holding reply to a vendor; a first-pass agenda note | The EA edits. You approve anything with a commitment, an amount or a name. A named person sends, because Copilot can’t send on your behalf yet. |
| 3. Commit | Nothing. It may prepare inputs only. | Accepting a meeting, approving spend, telling someone something in your name | You, or a person you named in advance |
A suggested split, written for a CEO and EA. Adjust the examples to your own risk.
Copilot can draft in your name, and a named person sends it.
The levels change with the seat, so here’s who they land on differently:
Here’s the whole idea on one filled page: a Delegation Agreement for a single job, the Monday brief. It takes ten minutes to write. The two rows I’d fill in first are what it must not touch and who checks, because they’re the ones you’ll reach for on the day something goes wrong.
| Field | Agreed answer |
|---|---|
| Job | A one-page brief in the CEO’s inbox by 7:30 every Monday: decisions needed, people waiting, calendar collisions. |
| Who prompts | The EA, in the CEO’s delegated mailbox, from the EA’s own Microsoft Copilot licence. |
| Whose access it runs on | The EA’s, as granted by the CEO for the mailbox and calendar. Board and compensation folders sit outside it. |
| What Copilot may read | The CEO’s inbox and calendar for the last seven days. |
| What it must not touch | Anything in the people-matters or deal folders, and anything the EA wouldn’t open by hand for this job. |
| What the product can’t do yet | Send, triage or schedule in the delegated mailbox. So the EA sends and books, and Copilot only drafts. |
| Who checks, and how | The EA opens the source for every item marked “decision”. The CEO opens two items at random each week for the first six weeks. |
| Who sends on the CEO’s behalf | The EA, after the CEO’s yes. Drafts only until then. |
| Where it’s kept | The brief goes out as an email. Prompts and answers stay in the EA’s Copilot history, and the compliance owner knows that. |
| Review | First Monday of each quarter, ten minutes, both of you. |
A filled example for a CEO and EA. The product limits come from Microsoft’s July 2026 support page; every other row is a suggested setting.
Three prompts sit under that agreement. The first is your EA’s. The other two are yours or your chief of staff’s, and both work on things that already exist. With a Microsoft 365 Copilot licence the / menu can point Copilot at specific people, files, meetings and emails, while Copilot Chat users can reference files only.[7]
1. EA, in the executive’s delegated mailbox
Summarize emails from the last five days in the [CEO name] mailbox. Sort them under three headings: needs a decision from [CEO name], waiting on someone else, and for information only. For every item give the sender, the subject line and the date so I can open the original. Then list any clashes in [CEO name]’s calendar this week. End by telling me anything you couldn’t read.
2. CFO or CEO, before the board pack goes out
Compare /[Q4 board pack draft] with /[Q3 board pack]. List every number that changed, and every claim in the text that has no number on the page behind it. Then act as a director who read Q3 closely and give me the three hardest questions, with the slide each one is about.
3. Chief of staff, after the leadership meeting
From /[Tuesday leadership meeting], list what I agreed to do, who is waiting on it, and any date mentioned. Quote the line from the transcript behind each item. If nobody mentioned a date, say so.
Prompt 1 follows the shape of the example prompts on Microsoft’s delegated-mailbox page. Prompts 2 and 3 use the / menu to point Copilot at named files and meetings. Replace the bracketed parts with your own.
Look at the last line of prompt 1. Copilot can’t tell you about a folder it has no access to, so treat that sentence as a courtesy, not a check. The check itself comes further down, and the meeting prompt is one of several in our Copilot meeting prompts guide if you want more of them. If you’d rather have the executive’s own brief show up unprompted, scheduled prompts are the place to start.
Once the brief exists it has to move between two people without dragging the wrong files along. Copilot Pages and Copilot Notebooks are the two containers Microsoft gives you for that, and they behave differently.
A Page is one piece of work. When your EA shares a Page, you get that page and can contribute to it without gaining access to her Copilot chat session.[10] A Notebook is a workspace. Sharing it gives the recipient access to the files linked inside it, provided the sharer has sharing permission on each file, and chats inside a shared Notebook stay private to each person.[9] That’s a wider door than the word “notebook” suggests.
So the decision rule is small. Send a Page when your EA hands you a brief. Send a Notebook only when you’d be comfortable with the recipient opening everything linked inside it, such as a board-cycle workspace shared with your chief of staff. One boundary catches board work in particular: external guests can’t open shared Pages through a link, and Notebooks don’t support external sharing.[8] A non-executive director outside your tenant needs another route.
Before you share a Notebook, take ten minutes:
Say you’re the EA to a CFO. Your Monday brief says nothing is pending on the lease dispute, because you haven’t been added to the legal folder where that thread lives. The CFO reads “nothing pending” as a fact and skips a call. Nothing in the brief was wrong: Copilot answered from what you could see.
That’s the Access Rule from the other side. An absence in a brief only counts as evidence once someone with wider access has looked, which is why a check has to be more than a glance. Three checks cover most of it:
Anything you’d act on gets opened at its source by a person before it moves.
| What Copilot does | What the human still owns | How it gets checked |
|---|---|---|
| Sorts the last week of the CEO’s inbox into decision, waiting and information | Which items are truly decisions, and which the EA can close | EA opens the source for each decision item; CEO opens two at random |
| Compares the Q4 board draft with Q3 and lists what changed | Whether a change matters and what the board hears about it | CFO recomputes each changed headline number from the finance system |
| Drafts replies to a vendor thread | What’s promised and what’s conceded | EA reads the whole thread; CEO approves anything with an amount; a named person sends because Copilot can’t send on your behalf |
| Lists what the CEO agreed to in the leadership meeting | Whether each item is a real commitment | Chief of staff matches each item to the transcript line Copilot quoted |
An example split for four delegated jobs. Change the reviewer and the sampling rate to match your own risk.
One more question belongs here because executives ask it: who else can see the prompts? Microsoft says prompts and responses are stored alongside your organization’s other Microsoft 365 content, and that admins can search them with content search or Microsoft Purview.[4] The store is a hidden folder in the mailbox of the person running the AI app, searchable by eDiscovery, and what an app shows you isn’t a reliable guide to what’s retained.[5] Audit records also list the resources Copilot accessed, including the sensitivity label on each.[6]
Put that beside the delegate page’s statement that history goes to your assistant’s account, and the likely consequence is that a question about your mailbox lives in her mailbox, under her retention rules. That’s our inference, not a Microsoft statement. For a sensitive matter such as a restructuring, decide with your compliance owner beforehand whether it goes through Copilot at all.
A month in, the tempting metric is how many prompts your EA has run. A chief of staff can be given delegate access to the Copilot Dashboard,[11] but prompt counts describe activity rather than whether the Monday brief is doing its job. Our Use, Persistence and Impact lens fits a pair better, and you can run it in ten minutes a month.
| Step | Question for the pair | How to find out | Example at week eight |
|---|---|---|---|
| Use | Was the brief built to the agreement this week? | EA marks yes or no; CEO notes whether it arrived by 7:30 | 7 of 8 Mondays |
| Persistence | Is it still running when neither of you is chasing it? | Ask what would break if it stopped, and whether the chief of staff could run it | Ran in week six while the EA was away, from the written agreement |
| Impact | Is Monday better, and are the checks finding anything? | Minutes the CEO spends triaging before and after; a log of corrections | Triage from about 40 minutes to about 15; two corrections logged, both wrong dates |
Illustrative values for a CEO and EA, not client data.
Read the log carefully. A corrections log that stays empty for eight weeks has two possible meanings: the brief is solid, or the checks have gone perfunctory. You can’t tell which from the log alone, so keep the random sampling going.
Training builds the capability: your EA and chief of staff knowing how to ask for sources and what Copilot can’t see. The agreement is the workflow design, the place that capability lands. The monthly ten minutes is reinforcement, and adoption is what you see when the brief is still arriving in the spring. You can set all of this up between the two of you. A role-specific session for the people in the EA and chief of staff seats shortens the learning curve and gives a leadership team shared habits instead of one enthusiastic pair. Our Microsoft Copilot training guide covers what that looks like, and what makes an AI-powered professional different covers how the behavior change shows up.
This week, pick the one recurring job your EA already does in your inbox or calendar. Fill in the Delegation Agreement above in ten minutes, then open two sources from the next brief together.
Microsoft’s February 2026 support page says you must have a Microsoft Copilot licence to read or act on items in shared and delegate mailboxes, and it’s written about the person doing the reading. Nothing on the pages I read says the mailbox owner needs one too, so confirm that with your admin. Pages and Notebooks differ: a work or school recipient with SharePoint or OneDrive storage can open a shared Page without a Copilot licence, and Copilot Chat users can use shared Notebooks, but Teams and SharePoint sources inside them are limited to Microsoft 365 Copilot users.
Microsoft’s pages don’t list which Outlook clients show it, so start with the licence and the permission type: Full Access or folder-level. Then try the Microsoft Copilot app or the Copilot Chat page at m365.cloud.microsoft/chat, where the February page says you can name the mailbox in the prompt and use the / menu for name lookup, while the newer page says no special syntax is needed. Compare Outlook on the web with the desktop app before assuming anything is broken.
Not reliably. Users can delete their own Copilot activity history from My Account, but Microsoft says messages visible in an AI app aren’t an accurate reflection of what’s retained. Stored messages sit in a hidden mailbox folder that eDiscovery can search until they’re permanently deleted. Decide with your compliance owner which matters go through Copilot before anyone types, because deleting afterwards isn’t a substitute.
It depends on the rights, not the label’s name. Microsoft says that when data is encrypted with Purview Information Protection, applied through a sensitivity label or restricted permissions, Copilot honors the usage rights granted to the user. If your EA isn’t among the people the encryption allows, the document won’t come back in their answers, which is why a brief can quietly leave it out. The page I read doesn’t say what happens with a label that doesn’t encrypt, so ask your admin about that case.
Yes, if you hold access to the Copilot Dashboard and you assign them as a delegate. The delegate must be in the same tenant, must themselves have dashboard access, and sees the same insights you do but not your personal insights or recommended actions. You can assign up to 75 delegates, delegates can’t delegate onward, and admins can see delegation in audit logs. The page doesn’t state licence requirements for delegates, so check that with your admin.
Every Microsoft product statement here was read on Microsoft’s own Support, Learn or Purview pages in late September 2026, including the two support pages on delegated mailboxes (one updated July 2026, one dated February 2026) and the requirements page updated on 24 September 2026, where the wording on shared and delegate mailboxes has changed. Third-party summaries of Microsoft’s message center posts were deliberately not used. I couldn’t find a Microsoft page that lists which Outlook clients show Copilot in delegated mailboxes, or one that says whether the mailbox owner needs a licence, so this article doesn’t claim either. The example jobs, the levels, the agreement and the scorecard are our own suggestions.
Weekly tips. Real examples. Practical help for busy professionals.
We care about your data, check out our privacy policy.