What an RPMSG file is and why you can't open it like a regular document

An RPMSG file is an encrypted email message created by Microsoft Outlook. The "RPMSG" stands for "Rights-Managed Message" — these files are protected with restrictions that prevent them from being opened in most programs. You cannot simply double-click an RPMSG file and read it the way you would open a Word document or PDF.

RPMSG files are created when someone sends you an email with Information Rights Management (IRM) protection enabled. This protection is meant to control what you can do with the message — whether you can forward it, print it, or copy text from it. To open one, you need either the original email client that received it or specific software designed to handle encrypted Outlook messages.

The most common reason you have an RPMSG file sitting on your computer is that someone forwarded you a protected email as an attachment, or Outlook saved it separately when the original message couldn't be displayed normally.

Key Takeaways

  • RPMSG files are encrypted Outlook emails that require the original email account or special software to open.
  • Opening one in Outlook is the fastest method if you have the email account that received the original message.
  • If you do not have Outlook or the original account, third-party tools like eM Client or Outlook Message Viewer can sometimes read the file.
  • Some RPMSG files cannot be opened outside of Outlook because the encryption keys are stored only in that account.
  • If the sender used strong IRM protection, you may need to contact them and ask for an unprotected version of the message.

Opening an RPMSG file in Microsoft Outlook

If you have Microsoft Outlook installed and you are signed into the email account that originally received the protected message, this is your best option. Outlook knows how to decrypt the file because it has access to your account's encryption keys.

Open Outlook and go to File > Open > Open Outlook Data File (the exact menu path varies slightly between Windows and Mac versions). Navigate to the RPMSG file on your computer and select it. Outlook will decrypt and display the message. If Outlook asks for permission to open the file, click Yes or Allow.

If you are not signed into the account that received the original email, Outlook will not be able to decrypt it. You will need to either sign into that account first or try a different method.

Using Outlook Message Viewer if you do not have Outlook installed

Microsoft offers a free tool called Outlook Message Viewer that can open certain RPMSG files without a full Outlook installation. This tool is designed specifically for reading Outlook message files and works on both Windows and Mac.

Download Outlook Message Viewer from Microsoft's website (search "Outlook Message Viewer" in your browser). Install it, then open the program and use File > Open to locate your RPMSG file. The viewer will attempt to display the message contents.

This method has a limitation: if the RPMSG file is protected with strong IRM encryption, Outlook Message Viewer may not be able to decrypt it. The tool works best with RPMSG files that have basic protection or no protection at all.

Trying third-party email clients like eM Client

eM Client is a desktop email program that can sometimes open RPMSG files, particularly if the encryption is not extremely strict. It is available for both Windows and Mac. Download and install eM Client, then open the program and use its file import or open function to load the RPMSG file.

eM Client works best if you add your email account to the program first — this gives it access to your encryption keys, similar to how Outlook works. If you do not add your account, eM Client may still display the message but without the ability to decrypt protected content.

Other email clients like Thunderbird do not natively support RPMSG files, so eM Client is one of the few third-party options worth trying.

What to do if the file will not open in any program

If you have tried Outlook, Outlook Message Viewer, and eM Client without success, the RPMSG file is likely protected with encryption that requires the original email account and Outlook to open. This is by design — the sender used strong IRM protection specifically to prevent the message from being read outside of a controlled environment.

Your options at this point are limited. You can contact the person who sent you the RPMSG file and ask them to resend the message without IRM protection, or ask them to copy the message content and send it to you as plain text or in a different format. Many organizations use IRM protection for sensitive documents, and the sender may be able to provide an unprotected version if you explain why you need it.

If the sender is no longer available or unwilling to help, the file may not be readable to you. This is the intended outcome of strong IRM protection.

Checking what protection is on your RPMSG file

Before you spend time trying different programs, you can get a sense of how protected the file is. Right-click the RPMSG file and select Properties (Windows) or Get Info (Mac). Look at the file size and creation date — these tell you when the file was created but not what protection is on it.

The only reliable way to know what protection level the file has is to try opening it. If Outlook opens it without asking for additional permissions, the protection is light. If Outlook asks for special authorization or refuses to open it, the protection is strong.

Some RPMSG files are also corrupted or incomplete, which can prevent any program from opening them. If the file is very small (under 5 KB) or was partially downloaded, it may be damaged beyond repair.

Converting an RPMSG file to a readable format

Once you have successfully opened an RPMSG file in Outlook or another program, you can save the message in a different format. In Outlook, right-click the message and select Save As. You can save it as a .MSG file (which is less protected), a .TXT file (plain text), or even print it to PDF.

Saving to a different format removes some of the IRM restrictions, though the original sender's intent to protect the message should still be respected. If you save an RPMSG as a PDF or text file, you will have a version that opens in any program, but you lose the ability to reply to or forward the original message through Outlook.

This conversion method only works if you were able to open the RPMSG file in the first place. If the file is too heavily encrypted, you cannot convert it.

Frequently Asked Questions

Can I open an RPMSG file on my phone or tablet?

Not directly. RPMSG files are designed for desktop email clients like Outlook. If you have the Outlook mobile app and you are signed into the account that received the original email, you might be able to view the message through the app, but you cannot open an RPMSG file as an attachment on a phone.

Why did Outlook save my email as an RPMSG file instead of showing it normally?

This usually happens when Outlook cannot decrypt the message in real time, often because you are not signed into the correct email account or the IRM protection is preventing normal display. Outlook saves it as an RPMSG file so you can try to open it later when the right account is active.

Is it safe to open an RPMSG file from someone I do not know?

RPMSG files themselves are not a common vector for malware, but the message inside could contain malicious links or attachments. Treat them the same way you would treat any email from an unknown sender — do not click links or download attachments unless you are certain they are legitimate.

What if the sender is my company and they say I have to open it?

Ask your IT department or help desk. They can either provide you with the correct email account access, send you an unprotected version, or give you a tool that your company uses to read protected messages. Many organizations have internal solutions for IRM-protected emails.

Can I remove the IRM protection from an RPMSG file myself?

No. IRM protection is encrypted at the server level, and there is no legitimate way to remove it without the encryption keys. If you need the protection removed, you must contact the sender or the organization that applied it.