To encrypt an email in Outlook, start a new message, open the Options tab and select Encrypt, then choose Encrypt or Do Not Forward before you send. That option comes with a Microsoft 365 Personal or Family plan or a work account that has it switched on. Work accounts may also offer S/MIME, which needs a digital certificate.
Sending a contract, bank details or a client's personal information by ordinary email always feels a bit like posting a postcard. Outlook can lock the message so only the right person can read it, and the recipient doesn't need Outlook to open it. The catch is that the options depend on your account. Here's which encryption you've got, how to use it, and what your recipient will see.
Encrypt an email in Outlook, step by step
- Click New mail to start a message.
- Add your recipient, subject and message as usual.
- Select the Options tab on the ribbon.
- Select Encrypt, then choose Encrypt or Do Not Forward.
- Send the email.
To take encryption off a message before you send it, go back to the same menu and choose No permission set, which Microsoft says is the default.
Encrypt or Do Not Forward?
| Option | What it does | Use it for |
|---|---|---|
| Encrypt | Keeps the message encrypted inside Microsoft 365 | Sensitive details you're happy for them to save |
| Do Not Forward | Encrypted, and the message can't be copied or forwarded | Confidential material that must stay with one person |
| No permission set | Default; encrypts the connection with the recipient's provider where possible | Everyday email |
One detail worth knowing with Do Not Forward: Microsoft says Office attachments such as Word, Excel and PowerPoint files stay encrypted even after they're downloaded, but PDFs and images can be downloaded without encryption. If the attachment is the sensitive part, send it as an Office file or think about whether email is the right channel at all.
Who gets the Encrypt button?
Microsoft describes the Encrypt option for people with a Microsoft 365 Family or Personal plan using Outlook.com or new Outlook, and for work or school accounts where the organisation has it enabled. If you don't see it, you're probably on a free account or an account where your administrator hasn't turned it on. That's the single most common reason people can't find it.
What your recipient sees
- Outlook.com or Microsoft 365 users read and reply as normal, as if it weren't encrypted at all.
- Gmail or Yahoo users get an email with instructions and can sign in with their Google or Yahoo account, or use a temporary passcode.
- Other providers, such as Comcast or AOL, use a temporary passcode that's sent to them by email.
I always send a quick heads-up first: "I'm sending the contract encrypted, you'll get a link to open it." It stops people deleting it as a phishing attempt, which, to be fair, is exactly what a surprise secure message looks like.
S/MIME for work accounts
Some businesses use S/MIME instead, an encryption standard based on digital certificates. Microsoft explains that S/MIME needs the recipient to open the message with a certificate on their computer. In new Outlook you'll find it under Options, then More Options, then Encrypt this message (S/MIME). Microsoft adds that to send S/MIME encrypted email to someone outside your organisation, you must install their certificate first, and if you request a receipt you must also digitally sign the message.
The alternative many organisations use, Microsoft Purview Message Encryption, is easier for recipients. Microsoft says it can be read directly in new Outlook, Outlook on the web, the Outlook mobile apps and Outlook for Windows 2019 and newer, while people on other services get instructions to open it.
Encrypting is not the same as recalling
Encryption protects a message on its way and once it arrives. It doesn't let you take it back. If you've sent something sensitive to the wrong person, encryption won't save you, so double-check the address before you send. Turning on a short undo send delay in your Outlook settings gives you a few seconds to catch mistakes.
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A simple routine for sensitive emails
- Ask yourself whether the person needs the details in writing at all.
- Check the recipient's address letter by letter.
- Send a short warning that an encrypted email is on its way.
- Choose Do Not Forward for anything that must stay with one person.
- Delete the draft and any copies you no longer need.
When email isn't the right tool
Encrypted email is brilliant for a one-off contract or a set of bank details. If you're regularly exchanging sensitive files with clients, a shared folder with tight permissions is often safer and easier to manage than a chain of encrypted messages. And if you're deciding what format to send a contract in, remember the attachment point above: my guide to converting Word to PDF is handy, but a PDF loses its protection once it's downloaded from a Do Not Forward email. If you're tightening up how your business sends email generally, see why fewer small business emails get read.
My verdict
New mail, Options, Encrypt, then pick Encrypt or Do Not Forward. If the button's missing, check your account type before anything else. Warn your recipient that a secure message is coming, and remember Do Not Forward doesn't protect PDFs or images once they're downloaded.
Frequently asked questions
Why can't I see the Encrypt button in Outlook?
Encrypt is available with Microsoft 365 Personal or Family plans and on work or school accounts where it's enabled. Free accounts and some work accounts won't show it.
Can someone with Gmail open an encrypted Outlook email?
Yes. They get instructions and can sign in with their Google account or use a temporary passcode.
What does Do Not Forward do in Outlook?
It keeps the message encrypted and stops it being copied or forwarded. Office attachments stay encrypted even after download.
How do I remove encryption from an Outlook email?
Before sending, open Options, Encrypt and choose No permission set.
What is S/MIME in Outlook?
S/MIME is certificate-based encryption used by some organisations. The recipient needs a certificate to read the message.
