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How to encrypt an email in Outlook

A step-by-step guide for sending secure emails in Outlook.
February 13, 2023

Have you ever wanted to send an email that’s just between you and the recipient without anyone snooping in between? Then encryption is the solution for you. Don’t worry; it’s not as complicated as rocket science (unless you’re sending an email to astronauts, then it might be). We’ll show you how to encrypt an email in Outlook and keep your secrets, well, a secret! Ready to get started? Let’s dive in.

Read more: How to create an email group in Outlook


To encrypt an email in Outlook, select Options -> Encrypt and choose your preferred encryption setting before sending your message.


All the ways Outlook can encrypt your email and why they matter.

First of all, it’s essential to understand what encryption is. Encryption is the process of converting plain text into a coded language to protect it from unauthorized access. Essentially, it’s like locking your diary with a key and only giving it to the person you trust.

Learn more: What is encryption, how to use it, and why it matters

Encrypting an email message in Outlook converts it from readable plain text into scrambled cipher text. Only the recipient with the private key that matches the public key used to encrypt the message can decipher the message for reading. Therefore, any recipient without the corresponding private key will see indecipherable text. This ensures the confidentiality and privacy of email messages so that only the sender and the intended recipient can read them.

Methods to Encrypt Email in Microsoft Outlook

Outlook provides several methods for encrypting email messages, including:

  • S/MIME (Secure/Multipurpose Internet Mail Extensions)
  • Office 365 Message Encryption
  • Encrypt-Only
  • Rights Management Services (RMS)

Each method has its advantages and disadvantages, and the one you choose depends on your specific needs. S/MIME is widely used and provides end-to-end encryption, but it requires a digital certificate. Office 365 Message Encryption is a cloud-based solution that allows for secure email communication, even with non-Outlook users. Encrypt-Only is a simple method that encrypts a single message, while RMS is more complex and allows for granular control over email access and rights.

If you have an Office 365 subscription, you’ll see the following options:

  • Encrypt: Your message stays encrypted and doesn’t leave Microsoft 365. Recipients with and Microsoft 365 accounts can download attachments without encryption from, the Outlook mobile app, or the Mail app on Windows. You can use a temporary passcode to download the attachments from the Microsoft 365 Message Encryption portal if you use a different email client or another email account.
  • Encrypt and Prevent Forwarding: Your message stays encrypted within Microsoft 365 and can’t be copied or forwarded. Microsoft Office attachments such as Word, Excel, or PowerPoint files remain encrypted even after downloading them. Other attachments, such as PDF or image files, can be downloaded without encryption.

How to encrypt emails in the Outlook desktop app

First, compose an email on Outlook and choose Options. Select Encrypt, and pick the encryption with the restrictions you want to enforce, such as Encrypt-Only or Do Not Forward.

outlook app encrypt
Adam Birney / Android Authority

Encrypting with S/MIME

If you choose S/MIME, you must have a digital certificate installed on your computer. To set up encrypting with S/MIME, open Outlook, and under the File menu, select Options Trust Center > Trust Center Settings.

trust center settings office
Adam Birney / Android Authority

In the left pane, select Email Security. Under Encrypted email, select the S/MIME certificate.

outlook email security settings
Adam Birney / Android Authority

You can also select other encryption preferences from here, such as encrypting attachments or adding a digital signature for outgoing messages. Choose OK when done.

How to encrypt emails on the Outlook website

To send an encrypted message using the Outlook web browser, click the Encrypt button along the top bard after composing an email. Choose one of the two options: Encrypt or Encrypt and Prevent Forwarding.

outlook browser encrypt
Adam Birney / Android Authority

Encrypting emails in Microsoft Outlook helps secure the confidentiality of your communications. By encrypting your emails, you can rest assured that your messages and attachments are secure and protected from unauthorized access.

Read more: How to add Google Calendar to Outlook


Yes, Microsoft Outlook uses Transport Layer Security (TLS) to encrypt email messages in transit. TLS is a widely-used protocol for securing internet communications and is used by many email providers to encrypt emails as they travel from one email server to another. When you send an email using Microsoft Outlook, the message is encrypted while in transit, providing a secure means of transmitting sensitive information over the internet.

If you encrypt an email in Outlook, then all attachments to that email will also be encrypted. However, there are a few differences depending on which encryption option you choose.

If you choose the Encrypt option, recipients with Outlook and Microsoft 365 accounts can download attachments without encryption. If you select the Encrypt and Prevent Forwarding option, only Office attachments such as Word, Excel, or PowerPoint files remain encrypted even after they’re downloaded. All other attachments, such as PDF or image files, can be downloaded without encryption.

Yes, replies to encrypted emails in Microsoft Outlook are typically also encrypted. However, the reply may not be encrypted if the sender or recipient uses an email client that does not support the same encryption method.

Yes, Gmail can receive encrypted emails sent from Microsoft Outlook. Gmail supports the S/MIME (Secure/Multipurpose Internet Mail Extensions) encryption standard, which Microsoft Outlook uses for email encryption. When an encrypted email is sent from Microsoft Outlook to Gmail, Gmail can decrypt the email and display its contents to the recipient.