Why Gmail Shows RPMSG as an Attachment

When a Microsoft Outlook user sends you an IRM-protected email, Gmail receives the content but can't decrypt it — Gmail has no integration with Microsoft's Rights Management Services. So instead of showing you the email body, Gmail shows you a message.rpmsg file as an attachment.

The correct way to access the content isn't to open the attachment directly — it's to use one of Microsoft's authentication methods to prove you're the authorized recipient.

Gmail (Web Browser) — Step by Step

Method A: Click "Read the message" (The Standard Way)

  1. Open Gmail in your browser (desktop or mobile browser)
  2. Open the email containing the RPMSG attachment
  3. Look carefully at the email body — there's usually a blue button or text link that says "Read the message"
  4. Click it — this opens Microsoft's Office Message Encryption (OME) viewer in a new tab
  5. You'll see an authentication prompt. Choose your method:
    • One-time passcode: Microsoft sends a code to your email address. Enter it to view the message.
    • Sign in with Google: Authenticate using your Google account (works if your org has set up federation)
    • Sign in with Microsoft: Use your personal or work Microsoft account
  6. After successful authentication, the decrypted message displays in the browser
Don't see the "Read the message" button? The sender may have sent only the raw .rpmsg file without the OME wrapper. Try Method B below.

Method B: Access via Outlook Web App

  1. In a new browser tab, go to outlook.live.com
  2. Sign in with the same email address that Gmail is configured for (this works if your Gmail address is also your Microsoft account, or if you've added it to Outlook.com)
  3. Alternatively — if this is a work email — go to your organization's webmail portal (usually mail.yourdomain.com or outlook.office.com)
  4. Find the original protected email and open it there — OWA handles the decryption

Gmail App (Android & iPhone)

The Gmail mobile app works similarly to the web version:

  1. Open the Gmail app and find the protected email
  2. Tap the email to open it
  3. Look for the "Read the message" button in the email body
  4. Tapping it opens your phone's browser and loads the Microsoft OME viewer
  5. Authenticate via one-time passcode or Microsoft sign-in
  6. The decrypted message displays in the browser on your phone

If there's no "Read the message" button and you can only see the .rpmsg attachment, the best option is to switch to the Outlook app (see below).

Opening RPMSG on iPhone (iOS)

Option 1: Microsoft Outlook App (Recommended)

  1. Download Microsoft Outlook from the App Store (it's free)
  2. Open the app and add your email account (tap the + icon to add an account)
  3. Outlook supports adding Gmail, Yahoo, Exchange, and other account types
  4. Navigate to the inbox and find the original protected email
  5. The Outlook app has native IRM support and will display the protected content after verifying your identity with Microsoft's servers

Option 2: Safari + Microsoft OME Viewer

  1. Open the email in the Mail app (or Gmail app)
  2. Tap "Read the message" — this opens Safari with the OME viewer
  3. Request a one-time passcode to be sent to your email
  4. Check your email for the code, return to Safari, enter it
  5. The message displays in Safari

Opening RPMSG on Android

Option 1: Microsoft Outlook App (Recommended)

  1. Install Microsoft Outlook from Google Play (free)
  2. Add your email account to the app
  3. Navigate to the protected email in your inbox
  4. Outlook for Android handles IRM decryption natively

Option 2: Chrome Browser + OME Viewer

  1. Open the email in the Gmail app or Gmail mobile web
  2. Tap "Read the message"
  3. Chrome opens the Microsoft OME viewer
  4. Choose one-time passcode or sign in with Google/Microsoft
  5. Message displays in Chrome

Troubleshooting Common Mobile Issues

"Read the message" opens a blank page

Try clearing your browser cache and cookies, then try again. Alternatively, open the link in a different browser (Chrome vs Safari vs Firefox).

One-time passcode isn't arriving

Check your spam/junk folder. The passcode email comes from [email protected] with subject "Your one-time passcode." Allow 2-3 minutes for delivery. If it still doesn't arrive, try requesting it again.

Outlook app says "This message is protected" but won't decrypt

Make sure you're signed in to the Outlook app with the same account the protected email was sent to. Go to Settings in the app and verify the account identity. If using a work email, your IT admin may need to enable IRM for mobile access.

Downloading the .rpmsg file to your phone doesn't help

Opening a .rpmsg file directly from the Files app or Downloads folder won't work — no phone app can decrypt it without Microsoft authentication. You must go through the OWA or OME Viewer flow described above.