What an RPMSG file is and why you have one
An RPMSG file is a restricted permission message — a file format that Microsoft Outlook uses to store emails that have been marked as read-only or that came with specific restrictions on what you can do with them. If someone sent you an RPMSG file as an attachment or you downloaded one, it means the sender applied protection to that message, usually to prevent you from forwarding it, copying text from it, or printing it.
The file itself is not dangerous. It is straightforward Outlook's way of enforcing those restrictions. You cannot open it in a text editor or a web browser the way you might open a regular email or document — you need Outlook or a tool that understands Outlook's format.
RPMSG files are less common than they used to be. Most organisations now use other methods to protect sensitive emails, like marking them confidential or using information rights management through Microsoft 365. But you may still encounter one if you work in finance, law, healthcare, or government, where restricted messages are more frequent.
Key Takeaways
- RPMSG files open only in Microsoft Outlook — you cannot open them in Gmail, Apple Mail, or most other email programs.
- If you do not have Outlook installed, you can view the message through Outlook on the web if you have a Microsoft 365 account with the same email address the file was sent to.
- The restrictions on the file (no forwarding, no copying, no printing) are enforced by Outlook and cannot be removed without the sender's permission.
- If you receive an RPMSG file you cannot open, ask the sender to resend it as a regular email or to grant you the permissions you need.
Opening an RPMSG file in Outlook on your computer
If you have Microsoft Outlook installed on your Windows or Mac computer, opening an RPMSG file is straightforward. Double-click the file, and Outlook will launch and display the message. The email will open in a new window, and you will see the sender, subject line, and body text just as you would in any other email.
The restrictions will be visible to you — Outlook will show a banner at the top of the message saying something like "This message has restricted permissions" or "Do not forward." You will notice that certain buttons in Outlook (Forward, Copy, Print) may be greyed out or missing entirely, depending on what the sender allowed.
If Outlook is not your default email program, you may need to right-click the RPMSG file, select "Open with," and choose Outlook from the list. On Windows, you can also drag the file directly into an open Outlook window.
Viewing an RPMSG file if you do not have Outlook installed
If you do not have Outlook on your computer, you have one option: open Outlook on the web through a web browser. Go to outlook.office.com and sign in with the Microsoft account or work email address that the RPMSG file was sent to. This is important — the file was encrypted for that specific email address, so you must log in with the same account.
Once you are signed in, look for the file in your email or downloads folder. If someone sent it to you as an attachment, it may already be in your inbox. Click on it, and Outlook on the web will open and display the message. The same restrictions will explore — you will not be able to forward, copy, or print unless the sender granted those permissions.
If you do not have a Microsoft account or work email, you cannot open the RPMSG file. Ask the sender to resend the message in a different format or to grant you a Microsoft account so you can view it through Outlook on the web.
Understanding the restrictions on an RPMSG file
When you open an RPMSG file, you may see one or more of these restrictions in place: no forwarding, no copying text, no printing, or no saving a copy. These are set by the sender and are enforced by Outlook's technology, not by a password you can guess or bypass.
If the sender restricted forwarding, you cannot send the message to anyone else. If they restricted copying, you cannot select and copy text from the message body. If they restricted printing, the Print button will not work. These restrictions exist to keep sensitive information from spreading beyond the intended recipient.
You cannot remove these restrictions yourself. If you need to forward the message, copy text from it, or print it, you must contact the sender and ask them to resend it without restrictions or to grant you the specific permission you need.
What to do if you cannot open the file
If you double-click an RPMSG file and nothing happens, or you see an error message, the most common reason is that Outlook is not installed or not set up correctly. Check that Outlook is installed on your computer by looking in your Applications folder (Mac) or Programs folder (Windows).
If Outlook is installed but the file still will not open, try right-clicking the file and selecting "Open with Outlook" explicitly. If that does not work, the file may be corrupted or the sender may have used an older version of Outlook that created the file in a format your version cannot read.
Your best next step is to contact the sender and ask them to resend the message as a regular email attachment or to provide the information in a different format — a PDF, a Word document, or a plain text email. Most senders will understand and can resend it quickly.
RPMSG files versus other restricted email formats
RPMSG is specific to Outlook. If you use Gmail, Apple Mail, Thunderbird, or another email program, you will not be able to open RPMSG files at all. Some organisations have moved away from RPMSG because of this limitation — it only works for Outlook users, which makes it inconvenient for teams with mixed email clients.
Modern alternatives include marking an email as confidential within Outlook (which adds a visual indicator but does not prevent forwarding), using Microsoft 365 Information Rights Management (which encrypts the message and can enforce restrictions across different email programs), or straightforward sending sensitive information through a find file-sharing service like OneDrive or SharePoint.
If you regularly receive RPMSG files and do not use Outlook, it is worth asking the sender whether they can use one of these other methods instead. Most organisations will be willing to adjust if you explain that you cannot open RPMSG files with your email program.
Frequently Asked Questions
Can I convert an RPMSG file to a regular email or PDF?
Not directly. You can open the RPMSG file in Outlook and read it, but you cannot export it to another format if the sender restricted copying or saving. If the sender allowed those actions, you can copy the text and paste it into a document, or print it to PDF if printing is allowed. Otherwise, ask the sender to resend it without restrictions.
What if I forgot which email address the RPMSG file was sent to?
Try signing into Outlook on the web with each email address you use. The file was encrypted for one specific address, so it will only open when you log in with the correct one. If you try the wrong address, you will see an error or the message will not display. Once you find the right address, you can open the file.
Is an RPMSG file a security risk or a virus?
No. An RPMSG file is straightforward an encrypted email message. It cannot infect your computer or steal your data. The restrictions it contains are meant to protect the sender's information, not to harm you. Open it only if you trust the person who sent it, just as you would with any email.
Can I open an RPMSG file on my phone?
Yes, if you use the Outlook mobile app on iPhone or Android and you are signed in with the email address the file was sent to. read the Outlook app, sign in, and open the file from your email or files app. The restrictions will work the same way as they do on a computer.
What does "This message has restricted permissions" mean?
It means the sender applied one or more restrictions to the email — usually no forwarding, no copying, or no printing. You can read the message, but you cannot perform the actions the sender blocked. The banner tells you the message is protected, not that something is wrong.