To view the message on your computer...
Save and open the attachment (message.html), and then follow the instructions from there.
To view the message on an iPhone or iPad...
Open the message again, tap and hold the attachment, and select Open in OME Viewer.
If you don't have the OME Viewer app, download it now.
To view the message on an Android device...
Open the message again, tap the attachment, and select OME Viewer.
If you don't have the OME Viewer app, download it now.
To view the message, sign in with a Microsoft account, your work or school account, or use a one-time passcode.
To view the message, sign in using a one-time passcode.