What is an RPMSG File and How to Open It?

An RPMSG file usually appears when someone sends you a protected or encrypted email through Outlook. That is why the attachment often feels confusing or refuses to open like a normal file. 

Microsoft uses the .rpmsg format to restrict access, forwarding, copying, or printing of sensitive emails. I have created this guide to explain what an RPMSG file type is, how to open it in different email clients, and what to do if it won’t open properly. 

Quick Answer: How to open RPMSG files?

• Open the RPMSG file in Microsoft Outlook or Outlook Web and sign in with the authorized Microsoft account if prompted.
• If you received the file in any other email client, open the protected message link inside the email and verify your identity using a one-time passcode or email sign-in.

What is a .rpmsg File?

A .rpmsg file is a protected email message created through Microsoft’s Information Rights Management (IRM) and encryption system. The format is primarily used in Outlook and Microsoft 365 environments to secure sensitive emails and limit recipients’ ability to modify them.

For example, the sender may block forwarding, copying, printing, or downloading attachments. That is why RPMSG (Rights Protected Message) files usually appear in business or corporate emails.

The concept is somewhat similar to WhatsApp’s end-to-end encryption. In simple terms, it is not a normal attachment. It is a permission-controlled message designed to protect your online privacy and confidential information. 

It used to send encrypted emails in Outlook. Even if you receive the file, you still may not have permission to open it unless your account matches the sender’s protection settings.

How to open an RPMSG file?

The easiest way to open an RPMSG file is through Microsoft Outlook or Outlook Web. The process depends on the sender’s protection rights, your email provider, and whether your account has permission to access the message.

How to Open an RPMSG File in Outlook?

Outlook is the smoothest and most reliable choice for opening RPMSG files. Here’s how to do that:

• Open Microsoft Outlook.
• Open the email containing the .rpmsg attachment.

  

• Double-click the RPMSG file if needed.
• Now, just sign in with the authorized Microsoft account if prompted.

Protected emails in Outlook often behave like regular emails, but you may see restriction notices at the top of the message. Also, remember that RPMSG permissions are tied to identity. Having the file alone does not guarantee access. 

How to Open RPMSG Files in Gmail, Yahoo, or Other Email Clients?

This is where most users get confused. Other email clients, like Gmail and Yahoo, do not have a direct RPMSG viewer like Outlook. Instead, Microsoft typically includes a protected-message link inside the email.

Here’s how to open .rpmsg files on other email clients:

• Open the email containing the protected message.
• Next, click on Read the message or a similar option.

  

• Sign in with your email account or request a one-time passcode.

  

• Verify your identity and open the protected message in your browser.

Keep in mind that one-time passcodes usually expire after a short time, which is why a delayed verification attempt may fail.

What to Do If an RPMSG File Will Not Open?

Most RPMSG problems are related to permissions or compatibility, not file corruption. Here are the most effective fixes you can try:

1. Verify the Correct Email Account: Make sure you are signed into the same email address that originally received the protected message. Using the wrong account is one of the most common reasons files stay locked.
2. Try Outlook Web: In many cases, Outlook Web opens protected messages more reliably than older desktop Outlook versions. If the desktop app fails, try opening the email directly through your browser.
3. Update Outlook: Older Outlook builds may struggle to decrypt newer protected messages properly. Updating Outlook can fix attachment errors and compatibility issues.
4. Enable IRM Permissions: If your account belongs to a company or organization, IRM may need to be enabled by the administrator before protected emails can open correctly.
5. Install Microsoft Purview or Azure Information Protection Tools: Some organizations use Azure Rights Management protection. In those situations, installing Microsoft Purview Information Protection Viewer and the Azure Information Protection client may help you.
6. Ask the Sender to Resend the File: If nothing works, ask the sender to resend the message without encryption, as a PDF, or with regular attachments instead.

If the file itself is damaged or incomplete, even Outlook may fail to open it. In that case, you should ask the sender to resend the original email.

Conclusion

RPMSG files exist to protect sensitive emails, not to make them difficult to open. Once you understand that the format is tied to Microsoft’s protection system, all of this starts making sense.

Outlook usually handles the RPMSG format automatically, while Gmail and other clients often require additional verification steps. And remember, if your account, software, or verification method does not match the sender’s settings, the message may remain locked.