You can draft email with Copilot in Outlook in about four seconds, which is roughly three seconds less than it takes to read what it wrote. That gap is where the trouble lives.
Most guides to this feature stop at where the button is. This one covers the two things people actually get stuck on: why the button is missing, and which sentences in the draft deserve a second look before the message leaves your outbox.
Short answer: Open a new message, select Copilot on the ribbon, choose Draft with Copilot, and describe what you need to say. If the option is greyed out or absent, the most common documented cause is that you are composing in plain text rather than HTML. Before sending, reread only the sentences that commit you to something. Verified against Microsoft’s documentation on 31 August 2026.
Why the Copilot Button Is Missing
This is the question that sends people to search, and the answer they usually find is some version of wait for the rollout. Microsoft documents four specific situations, and only one of them is something you can change in thirty seconds.
Plain text messages are not supported
Microsoft states it plainly: Draft with Copilot does not support messages composed in plain text format. If your Outlook is set to compose in plain text, the feature has nothing to attach itself to.
The fix sits under Settings, then Mail, then Compose and reply, where you select HTML from the dropdown. People who inherited a locked-down profile, or who switched to plain text years ago to solve a signature problem, tend to have forgotten this is even a setting.
Shared, delegate and group mailboxes
Copilot features are unavailable on archive mailboxes, group mailboxes, and shared or delegate mailboxes. That is not a temporary gap. It rules out the exact place where assisted drafting would help most, which is a support or enquiries address worked by several people.
If your job is answering a shared inbox, this single constraint decides your whole approach. You will not be drafting replies with Copilot there, so the automation available to you is rules, templates and quick steps.
Mailboxes outside Exchange Online
Copilot in Outlook does not work on mailboxes that are not hosted on Exchange Online. An on-premises Exchange mailbox, or a personal IMAP account you added to Outlook for convenience, will not show the feature no matter which licence you hold.
Legacy Outlook for Mac
Microsoft supports Copilot in Outlook only in the latest version of Outlook for Mac. Legacy Outlook for Mac is not supported. If you are on a Mac and toggled back to the old interface at some point, that toggle is your answer.
⚠️ Watch out: Three of these four cannot be worked around. Only the plain text one is a setting. Before raising a ticket asking why Copilot is missing, check which mailbox you are actually in, because a delegate mailbox looks identical to your own in the folder list.
What Copilot Is Actually Writing From
Draft with Copilot takes a prompt and produces a message. You get dropdowns for length and tone, and a Regenerate option that produces a different version of the same request. You can also change the prompt and generate again, which is usually the better move.
What comes back is fluent. Fluency is the feature and it is also the risk, because a well-formed business email has a shape, and the model fills that shape whether or not you supplied content for every part of it.
This is the same failure you get when you ask AI for a formula and it produces something syntactically perfect that references the wrong column. Our guide to writing Excel formulas with AI covers the spreadsheet version of the problem. In email the cost is higher, because a wrong formula can be corrected quietly and a sent message cannot.
The Sentences Worth Reading Twice
Rereading the whole draft is what everyone recommends and nobody does. A shorter habit works better, because it is specific enough that you will actually perform it.
Anything that commits you
Scan for future tense and for dates. I will send, we can deliver, you will have it by. These are the sentences that turn into obligations, and they are the ones a generated draft is most likely to add on its own initiative.
If you had not decided on a date before you opened Outlook, no date should appear in the message. That single rule catches most of it.
Every number and every date
A wrong number that looks researched is worse than an obviously missing one. Nobody queries a confident figure, which means it propagates into the next email, and from there into somebody’s forecast.
Names, companies and job titles
Cheap to verify and expensive to get wrong. If you prompted with a first name only, the draft may have supplied a surname to complete the greeting.
Apologies you did not intend
Generated business email is agreeable by default. It apologises for delays, accepts responsibility for misunderstandings, and softens positions you may have wanted to hold. In an ordinary exchange that is harmless. In a dispute about who owes what, an unprompted apology is a concession.
💡 Pro tip: Read the draft once for meaning, then run your eye down it looking only for verbs in future tense. It takes about fifteen seconds and it is the highest yield check you can make on a generated message.
Prompting So There Is Less to Fix
Everything the draft invents is something your prompt left open. That reframes prompt writing as a much simpler job than the advice usually makes it sound: state the decisions you have already made, and the model has fewer gaps to fill with plausible guesses.
Most weak prompts name a topic. Strong ones name an outcome. The difference shows up immediately in how much of the result you have to rewrite.
The fourth row is the one people find counterintuitive. Telling it not to give a reason matters, because an unprompted decline reads as abrupt to a language model and it will manufacture an excuse to soften the message. That excuse becomes something you have said.
💡 Pro tip: If a fact belongs in the message, put it in the prompt. Anything you leave out and still want present is something the draft will approximate, and approximations in email are quotable.
Encrypted and Labelled Mail Behaves Differently
Two documented behaviours catch people out in organisations that use information protection, and neither is obvious from the interface.
Copilot cannot process messages encrypted with S/MIME or Double Key Encryption. Signed, encrypted, rights-managed and certain labelled messages are unsupported for most features. If your team encrypts by default, the summarise and draft options will look broken when they are working exactly as documented.
The second one is subtler. Microsoft notes that the sensitivity level of a draft may change if the sensitivity assigned to the generated output is higher than the level on the draft. Your message can come back carrying a stricter label than the one you started with, which can change who is able to open it.
📊 Note: If you work somewhere that applies sensitivity labels automatically, check the label on the message after generating rather than before. It is one of the few settings that can change underneath you with no warning in the compose window.
Draft and Coaching Are Not the Same Button
Coaching by Copilot reviews a message you have already written and suggests adjustments to tone, clarity and reader sentiment. It runs on your words rather than replacing them, which makes it the more useful of the two for anything sensitive.
The distinction matters because the two features fail in opposite directions. Drafting gives you a competent message that may not be your position. Coaching leaves your position intact and tells you how it is likely to land.
For a difficult message, write it badly yourself and then coach it. You keep the content and get the delivery. For a routine message where you know exactly what needs saying, drafting saves the typing.
When to Leave It Alone
Some messages cost more to generate than to write, and they are recognisable in advance.
- Anything a lawyer might read later. Contract disputes, complaints, employment matters. Precision beats fluency, and you want every sentence to be one you chose.
- Very short replies. A two-line answer takes longer to prompt, generate and check than to type.
- Messages carrying a number you have not verified. Get the number first. Otherwise you are proofreading against nothing.
- Anything to somebody who knows how you write. A close colleague will notice the register change, and the message becomes about that instead of its contents.
The pattern behind those four is that assisted drafting saves typing, not thinking. When the typing is the small part of the job, there is not much left for it to save.
Common Questions
Why is Draft with Copilot greyed out in Outlook?
The most common documented cause is composing in plain text, since the feature does not support plain text messages. Change it under Settings, Mail, Compose and reply by selecting HTML. If you are in a shared, delegate, group or archive mailbox, or on a mailbox that is not hosted on Exchange Online, the feature is unavailable there permanently.
Does Copilot work in a shared mailbox?
No. Microsoft documents that Copilot features are unavailable on shared and delegate mailboxes, as well as group and archive mailboxes. Teams working a shared support address need rules, templates and quick steps instead.
Which Outlook versions support Copilot?
Outlook for Microsoft 365, Outlook for Microsoft 365 for Mac, new Outlook for Windows, Outlook for Android and Outlook for iOS. Legacy Outlook for Mac is not supported, and chat features are limited to new Outlook for Windows or Outlook on the web.
Can Copilot read encrypted email?
Not for S/MIME or Double Key Encryption. Signed, encrypted, rights-managed and certain labelled messages are unsupported for most Copilot features, so the buttons will appear to fail on mail that your organisation protects by default.
Can generating a draft change the sensitivity label on my message?
Yes. Microsoft notes the sensitivity level of the draft may change if the sensitivity assigned to the generated output is higher than the level on the draft. Check the label after generating rather than before.
What is the difference between Draft with Copilot and Coaching by Copilot?
Drafting writes a message from your prompt. Coaching reviews a message you already wrote and suggests adjustments to tone, clarity and reader sentiment. For difficult messages, writing it yourself and then coaching keeps your position intact.
What should I check in a Copilot draft before sending?
The sentences that commit you to something, every number and date, names and job titles, and any apology you did not intend. Future tense verbs are the fastest thing to scan for and they catch most of the risk.
The Short Version
- →A missing Copilot button is usually plain text composition, which is a settings fix.
- →Shared, delegate, group and archive mailboxes have no Copilot at all.
- →S/MIME and Double Key Encryption mail cannot be processed.
- →Generating can raise the sensitivity label on your draft.
- →Read the sentences that commit you. Future tense is the fastest scan.
- →Difficult message? Write it yourself, then use Coaching rather than Draft.