Outlook has two ways to encrypt an email, S/MIME and Microsoft Purview Message Encryption. S/MIME needs a certificate on your computer and a certificate from every outside recipient. Purview encryption works from Options and Encrypt. Microsoft states your account needs a qualifying Microsoft 365 subscription. Send a test message first.
Messages with contracts or personal data need protection on the way. Outlook includes two built in methods.
Steps follow the Microsoft Support page on sending encrypted emails in Outlook. Steps below apply to new Outlook for Windows.
How to Encrypt One Message With S/MIME?
- Open a new message and select Options then More Options.
- Tick Encrypt this message (S/MIME) and select OK.
- Select Send.
How to Encrypt All Messages With S/MIME?
Open Settings, Mail and S/MIME. Tick Encrypt contents and attachment for all messages I send and select OK. Microsoft states the setting also applies to replies and forwards.
How to Use Microsoft Purview Message Encryption?
- Select Options then Encrypt.
- Choose a restriction like Encrypt or Do Not Forward.
- Select Send.
Microsoft states recipients in new Outlook, Outlook on the web, Outlook mobile apps, Outlook for Windows 2019 and newer and Microsoft 365 can open these messages. Users of other mail services see instructions for opening the message.
What do You Need Before You Encrypt?
- Setup. Set up Outlook for encryption and digital signatures first.
- Certificates. Install the certificate of every outside S/MIME recipient on your computer. Recipients need a certificate on their computer too.
- Subscription. Your account needs a qualifying Microsoft 365 subscription.
- Server license. New Outlook works with Microsoft 365 Message Encryption only when the email server has an Office 365 Enterprise E3 license. Otherwise use S/MIME.
- No mixing. Do not apply Purview protection to a message already signed or encrypted with S/MIME.
Related reading: why a data breach needs DLP and what confidential information means.
Frequently Asked Questions
How do I Encrypt an Email in Outlook?
Select Options then More Options and tick Encrypt this message (S/MIME). Or select Options then Encrypt for Purview.
What is Required for S/MIME?
Your computer needs a certificate and so does every outside recipient.
Can I Encrypt All Outgoing Messages?
Yes. Tick Encrypt contents and attachment for all messages I send under S/MIME settings.
Does Encryption Need a Subscription?
Yes. Microsoft states your account needs a qualifying Microsoft 365 subscription.
Key Takeaways
- Outlook encrypts email with S/MIME or Microsoft Purview.
- S/MIME needs certificates on both computers.
- One setting encrypts all outgoing S/MIME messages.
- Purview needs a Microsoft 365 subscription.
- Do not mix S/MIME and Purview on one message.
Sources and References
Facts follow Microsoft Support.
- Send S/MIME or Microsoft Purview encrypted emails in Outlook (Microsoft Support) support.microsoft.com