Copilot drafts your emails, but the style is a compromise. With custom instructions you explain your way of writing once and from then on you get drafts that sound like you.
What are custom instructions?
Custom instructions are permanent rules that you give Copilot once, for example your preferred tone, the length you want or a particular greeting. As soon as you have saved them, Copilot applies these settings automatically to every new draft.
Think of it as a briefing for a new assistant: instead of explaining how you write with every request, you say it once and it remembers.
At a glance
- Set up once, active permanently
- Applies to new emails and replies
- Fully customisable: tone, length, greeting, sign-off, language
- Can be updated at any time
What you need
- A Microsoft 365 Copilot licence (not included in the basic M365 subscription)
- The new Outlook (Windows or Mac) or Outlook on the web, classic Outlook does not support this feature yet
- Check the top right in Outlook, the new interface is noticeably tidier
Step by step: how to set it up
- Open the Copilot settings in Outlook
- Tick the box «Use custom instructions when drafting emails»
- Add your instructions
- Save them
That's it. From now on Copilot in Outlook works to your rules, without you having to explain anything with every draft.
Check what Copilot produces
Now let Copilot draft a reply to an email. Then check whether the draft matches your style. Not happy yet? Keep adjusting your instructions, it is worth it.
What you can put in the instructions
There is no set structure. You can simply describe in natural language how you want to communicate.
Tone
«Always use a friendly but professional tone. Avoid overly formal language.»
Length
«Keep emails short, no more than 5 sentences for routine messages, more detailed only for complex topics.»
Greeting
«Start internal emails with ‹Hi [name]!› and external ones with ‹Dear [name]›.»
Sign-off
«End emails with ‹Kind regards, [your name]› and do not add a separate closing sentence, my signature takes care of that.»
Language
«Write in German unless the original email was in English, in which case reply in English.»
5 tips for better results
- Be specific: «Friendly» is vague. «Use the first name, keep the tone warm and end with a question», that is precise.
- Also say what Copilot should not do: for example «Do not use ‹as discussed› or ‹per my last email›.»
- Define length in measurable terms: instead of «short» go with «no more than 3 sentences for standard messages.»
- Test and refine: after saving, try a few drafts and adjust the wording if needed.
- Keep them current: new role, new style? Just go back into the settings and update your instructions.
Not sure which custom instructions to add?
This trick will help you along:
- Open a new chat in Copilot
- Run this prompt: «Analyse my last 200 emails and derive custom instructions for Copilot in Outlook from them that I can copy across word for word.»
- Copy the result into the custom instructions
- Test and refine it
Conclusion
Custom instructions are one of the most useful and least known features of Copilot in Outlook. Setting them up takes two minutes, the effect is permanent.
«Say once what you want. Copilot writes it that way forever.»
