How to Open Secure Email from Microsoft 365

by | Oct 9, 2025 | email

When you receive a secure email sent via Microsoft 365, the steps to open it depend on your email setup. Find your situation below and follow the corresponding instructions.

1. Internal Staff Member (Outlook with M365 Account)

If you’re part of the same organization:

  • You’ll receive the email normally in your inbox
  • The email will open just like any other message
  • Look for a banner at the top that says “This message is encrypted” or shows a lock icon
  • No additional steps are needed – you can read, reply, and forward the message as usual

2. External Recipient Using Outlook Desktop with M365 Account

If you use Outlook desktop app with a Microsoft 365 or Office 365 account:

  1. Open the email in your inbox
  2. The message will display normally with a banner indicating it’s encrypted
  3. You may see “This message is encrypted” at the top
  4. Click on the message body to read the full content
  5. You can reply and forward as normal

Note: Your Microsoft 365 account automatically handles the decryption, so no passcode is needed.

3. External Recipient Using New Outlook with M365 Account

If you use the new Outlook app with a Microsoft 365 account:

  1. Open the email from your inbox
  2. The encrypted message will open automatically
  3. Look for an encryption indicator (lock icon or banner) at the top
  4. Read the message normally
  5. Reply or forward using the standard buttons

Note: The new Outlook handles encrypted messages seamlessly when you’re signed in with your M365 account.

4. External Recipient Using Outlook for Web with M365 Account

If you access email through outlook.com or office.com:

  1. Sign in to your Outlook webmail
  2. Open the encrypted email from your inbox
  3. The message will display with an encryption notice at the top
  4. Read the email content normally
  5. Use Reply or Forward as you would with any email

Note: Being signed into your Microsoft account allows automatic access to encrypted messages.

5. External Recipient Using Outlook Desktop with Third-Party Account

If you use Outlook desktop with Gmail, Yahoo, or another non-Microsoft email:

  1. You’ll receive an email with the subject line and a message that says “You have received an encrypted message”
  2. Click the button that says “Read the message” or click the attachment labeled “message.html”
  3. You’ll be redirected to a Microsoft secure portal in your web browser
  4. Choose one of the sign-in options:
    • Sign in with Google (if you have a Gmail account)
    • Sign in with Yahoo (if you have a Yahoo account)
    • Sign in with Microsoft Account (if you have an Outlook.com account)
    • Use a one-time passcode (for any email address)

If using a one-time passcode:

  • Click “Sign in with a one-time passcode”
  • Check your email for a passcode (it arrives within minutes)
  • Enter the passcode on the secure portal page
  • Click Continue to read your message
  1. Once authenticated, you can read the message, download attachments, and reply

6. External Recipient Using Webmail with Third-Party Account

If you access Gmail, Yahoo, or other webmail through a browser:

  1. Open the email notification in your webmail inbox
  2. You’ll see a message stating “You have received an encrypted message”
  3. Click the “Read the message” button or link in the email
  4. Your browser will open the Microsoft Office 365 Message Encryption portal
  5. Choose your authentication method:
    • Sign in with your existing account (Google, Yahoo, Microsoft)
    • Request a one-time passcode (recommended for first-time users)

To use a one-time passcode:

  • Click “Sign in with a one-time passcode”
  • A passcode will be sent to your email address
  • Return to your inbox and find the passcode email (check spam if needed)
  • Copy the passcode
  • Return to the secure portal and paste the passcode
  • Click Continue
  1. View your secure message, reply if needed, or download attachments
  2. You can save the message or print it from the secure portal

Troubleshooting Tips

I didn’t receive a one-time passcode:

  • Check your spam/junk folder
  • Wait 5-10 minutes and check again
  • Try requesting a new passcode

The passcode doesn’t work:

  • Make sure you’re entering it exactly as received (copy and paste)
  • Passcodes expire after a short time – request a new one if needed
  • Ensure there are no extra spaces before or after the code

I can’t access the secure portal:

  • Try a different web browser (Chrome, Firefox, Edge, or Safari)
  • Disable browser extensions temporarily
  • Clear your browser cache and cookies

The link seems broken:

  • Don’t forward encrypted emails – the links are unique to you
  • Try copying the entire URL and pasting it into a new browser window
  • Contact the sender to resend the secure message

Need Help?

If you continue to have trouble accessing secure email, contact our office, we will help you work through any issues.

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