Microsoft 365 has a powerful security feature called Office 365 Message Encryption (OME) that enables organizations to securely send sensitive information by encrypting Outlook emails. Office 365 message encryption uses the capabilities of Azure Information Protection to send and receive encrypted email messages inside and outside your organization.
You should open an encrypted email using Outlook on Desktop or via browser (Office 365 Email) if the sender has allowed you to read the protected email.
There could be several reasons if a user is unable to open an encrypted Office 365 email.
When an encrypted message reaches an external recipient, he needs to authenticate to read its contents. If the recipient is already signed-in with his Microsoft account and uses Outlook, he will be able to read the email without further action. The email will contain an icon that is encrypted.
If the user uses another email platform (Gmail, iCloud, etc.), he will receive an email with an attachment (message.html):
You’ve received an encrypted message from email@example.com
To view your message
Save and open the attachment (message.html) and follow the instructions.
Sign in using the following email address: firstname.lastname@example.org
Follow the link to the Office 365 Message Encryption Portal (OME Portal) where you need to authenticate. The authentication method depends on the email client. You may be prompted for user credentials or a one-time code that will be sent to you with another message.
To view the message, sign in with a Microsoft account, your work or school account, or use a one-time passcode.
In some cases, when authenticating with a Microsoft account or one-time passcode, you may receive errors:
An error has occurred. We’re sorry. An unknown error has occurred. Please try again later.
Sorry, we can’t display your message right now. Something went wrong and your encrypted message couldn’t be opened. Please try again by following the instructions in the original email message in 5 minutes.
In this case, try to sign out of all Microsoft Office programs on your device, sign out your Microsoft account in your browser, restart your computer, and try to authenticate again.
If you want to use an iOS/Android mobile device to read emails, be sure to install and use Outlook for Mobile. The native iOS email app doesn’t support encrypted emails from Office 365.
When you receive an encrypted message in alternate alternative appl, you will see the following text (and the encrypted message file with the *.rpmsg extension — Rights-Managed Email Message will be attached to the email).
This message is protected with Microsoft Information Protection. You can open it using Microsoft Outlook, which is available for iOS, Android, Windows, and Mac OS. Get Outlook for your device.
Microsoft Information Protection allows you to ensure your emails can’t be copied or forwarded without your permissions.
If you cannot open an encrypted email using the desktop version of Outlook (2016/2019/365) or Outlook on the web, make sure you are connected to the Internet. The easiest way is to open your browser and browse any external site in it.