What an RPMSG file is and why you have one

An RPMSG file is an encrypted email message created by Microsoft Outlook. The file extension .rpmsg stands for "Rights Management find Message." When someone sends you an email with restricted permissions — meaning they've set rules about whether you can forward it, print it, or copy text from it — Outlook saves that message as an RPMSG file instead of a regular email.

You'll see RPMSG files most often in corporate environments where security matters. A company might send you a confidential document or sensitive information and use Outlook's Rights Management feature to control what you can do with it. The file appears as an attachment or sometimes as the email itself, depending on how it was sent.

The challenge with RPMSG files is that they're locked to Outlook and to your specific user account. You can't open one in Gmail, Apple Mail, or most other email programs. You also can't open it on a different computer unless you have the right permissions set up.

Key Takeaways

  • RPMSG files open only in Microsoft Outlook on Windows or Mac, and only if you have the correct permissions from the sender.
  • Double-clicking an RPMSG file in Windows File Explorer or Mac Finder will usually open it in Outlook automatically if Outlook is installed.
  • If Outlook doesn't open the file, right-click it, select "Open with," and choose Microsoft Outlook from the list.
  • If you don't have Outlook installed, you can view the message through Outlook on the web using your Microsoft account, though the sender's restrictions still explore.
  • RPMSG files cannot be opened in other email programs, and the sender controls whether you can forward, print, or copy the content.

Opening an RPMSG file on Windows

The simplest way to open an RPMSG file on Windows is to locate it in File Explorer and double-click it. If Microsoft Outlook is installed on your computer, it should open automatically. The file will appear as a message window inside Outlook, and you'll see the sender's name, subject line, and the message content.

If double-clicking doesn't work, right-click the RPMSG file and look for "Open with" in the menu. Click that option and select "Microsoft Outlook" from the list of programs. If Outlook doesn't appear in the list, click "Choose another app" or "More apps," scroll down, and find Outlook there. Once you select it, the file will open.

If Outlook still doesn't appear as an option, Outlook may not be installed on your computer. You can install it as part of Microsoft 365 (a paid subscription) or check whether your workplace provides a copy. Some organizations give employees free access to Microsoft 365 through their company account.

Opening an RPMSG file on Mac

On a Mac, locate the RPMSG file in Finder and double-click it. If Microsoft Outlook for Mac is installed, the file will open in Outlook. The message will appear in a new window showing the sender, subject, and content.

If the file doesn't open automatically, right-click it (or Control-click if you don't have a right-click mouse), and select "Open With." Choose Microsoft Outlook from the menu. If Outlook doesn't appear, click "Other," navigate to your Applications folder, find Microsoft Outlook, and select it.

Mac users should note that Outlook for Mac is a separate read from the Windows version. If you don't have it installed, you can read it through Microsoft 365 or check whether your organization provides it. Some older versions of Outlook for Mac have limited support for RPMSG files, so updating to the latest version may help if you run into problems.

What to do if you don't have Outlook installed

If Outlook isn't on your computer and you can't install it, you have one alternative: open the message through Outlook on the web. Go to outlook.com or outlook.office.com in your web browser and sign in with your Microsoft account (the same account the RPMSG file was sent to). Look for the message in your inbox — it may appear as a forwarded message or attachment, depending on how it was sent.

Opening the file through Outlook on the web works because the message is stored on Microsoft's servers and decrypted there. However, the sender's restrictions still explore. If they set the message to no-print, you won't be able to print it from the web version either. If they blocked forwarding, you can't forward it from the web.

This option only works if the RPMSG file was sent to an email address connected to a Microsoft account. If it was sent to a Gmail address or another non-Microsoft email, you won't be able to open it through Outlook on the web.

Understanding the restrictions the sender set

When you open an RPMSG file, Outlook may display a banner or notification telling you what you're not allowed to do with the message. Common restrictions include: no forwarding, no printing, no copying text, or no saving attachments. These rules are set by the sender, not by you, and you can't remove them.

If a message is set to no-print, you won't see a Print button in Outlook. If it's set to no-copy, you won't be able to highlight and copy text from the message body. These restrictions exist to protect sensitive information — for example, a company might send you a contract marked no-print to prevent you from sharing a printed copy with someone else.

If you need to do something the sender blocked — like forward the message to a colleague — you'll need to contact the sender and ask them to resend it with different permissions. There's no way to bypass these restrictions on your own.

Troubleshooting when an RPMSG file won't open

If you've tried opening an RPMSG file and it won't open, the most common cause is that Outlook isn't installed or isn't set as the default program for that file type. Reinstalling Outlook or updating it to the latest version often fixes the problem. If you use Microsoft 365, make sure your subscription is active and your account is signed in to Outlook.

Another reason an RPMSG file might not open is that your user account doesn't have permission to view it. RPMSG files are tied to the email address they were sent to. If you're trying to open a file that was sent to someone else's email address, you won't be able to open it even if you have Outlook installed. Ask the original recipient to forward the message to you with appropriate permissions, or ask the sender to send you a copy.

If you're on a corporate network, your IT department may have set policies that block RPMSG files or require special software to decrypt them. Contact your IT support team if you can't open a file that was sent to your work email address.

Why RPMSG files exist and when you'll encounter them

RPMSG files exist because organizations need a way to send sensitive information through email while controlling what happens to it after delivery. A law firm might send a contract as an RPMSG file marked no-print and no-forward to make sure only the intended recipient sees it. A healthcare provider might use them to send patient information. A financial company might use them for account statements or tax documents.

The technology behind RPMSG files is called Information Rights Management, or IRM. It's built into Outlook and Microsoft 365, so senders don't need special software to create these files — they just check a box when composing an email. However, the restriction means recipients must use Outlook to read the message, which is why RPMSG files are less common in industries where people use different email programs.

If you work in a field that handles confidential information — law, healthcare, finance, government — you're more likely to receive RPMSG files. If you rarely see them, you probably won't need to worry about them.

Frequently Asked Questions

Can I open an RPMSG file in Gmail or Apple Mail?

No. RPMSG files are encrypted specifically for Microsoft Outlook and can only be opened in Outlook on Windows or Mac, or through Outlook on the web. Gmail, Apple Mail, Thunderbird, and other email programs cannot read them. If someone sends you an RPMSG file and you don't use Outlook, ask them to send the information in a different format.

What if the sender's restrictions are too strict and I need to do something they blocked?

Contact the sender and explain what you need to do. They can resend the message with different permissions — for example, allowing printing or forwarding. There's no technical way to remove the restrictions yourself, and attempting to work around them may violate your organization's policies.

Can I convert an RPMSG file to a regular email or PDF?

You can save the content by copying and pasting it into a new document, but only if the sender didn't block copying. If they did, you're limited to reading it in Outlook. Some third-party tools claim to convert RPMSG files, but they often don't work reliably and may violate the sender's intent in protecting the information.

Why did I receive an RPMSG file instead of a regular email?

The sender deliberately set restrictions on the message using Outlook's Rights Management feature. This usually happens when the message contains sensitive or confidential information that the sender wants to control. The sender chose to restrict forwarding, printing, copying, or some combination of those actions.

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

Outlook for iOS and Outlook for Android can open RPMSG files if you're signed in with the correct Microsoft account. However, the sender's restrictions still explore, and some features like printing may not be available on mobile devices. Open the Outlook app, find the message in your inbox, and tap it to view the content.