MMF File Extension

What is MMF file?

MMF (Microsoft Mail message file) is a database file that contains email messages (inbox an outbox) for Microsoft NT Mail. MMF is an old format. MMF files were saved in Winnt35 folder on disk C. Each user had its own MMF file.

Processing MMF files

MMF format is no longer supported by model email software. However, user can use Microsoft Exchange Server to convert such a file into other formats. There have been cases where Outlook accepted MMF data after changing the file extension to PST and importing to the client despite the fact that those are two different data formats.

Programs which support MMF file extension

Below is a table that list programs that support MMF files. Files with MMF suffix can be copied to any mobile device or system platform, but it may not be possible to open them properly on target system.

Updated: 12/01/2023

How to open file with MMF extension?

Problems with accessing MMF may be due to various reasons. On the bright side, the most encountered issues pertaining to Microsoft Mail Message Format files aren’t complex. In most cases they can be addressed swiftly and effectively without assistance from a specialist. The list below will guide you through the process of addressing the encountered problem.

Step 1. Download and install Microsoft Mail

Problems with opening and working with MMF files are most probably having to do with no proper software compatible with MMF files being present on your machine. The most obvious solution is to download and install Microsoft Mail or one to the listed programs: Microsoft Exchange Server. Above you will find a complete listing of programs that support MMF files, classified according to system platforms for which they are available. One of the most risk-free method of downloading software is using links provided by official distributors. Visit Microsoft Mail website and download the installer.

Step 2. Update Microsoft Mail to the latest version

You still cannot access MMF files although Microsoft Mail is installed on your system? Make sure that the software is up to date. Sometimes software developers introduce new formats in place of that already supports along with newer versions of their applications. This can be one of the causes why MMF files are not compatible with Microsoft Mail. All of the file formats that were handled just fine by the previous versions of given program should be also possible to open using Microsoft Mail.

Step 3. Assign Microsoft Mail to MMF files

If the issue has not been solved in the previous step, you should associate MMF files with latest version of Microsoft Mail you have installed on your device. The method is quite simple and varies little across operating systems.

Change the default application in Windows

• Right-click the MMF file and choose Open with option
• Next, select the Choose another app option and then using More apps open the list of available applications
• The last step is to select Look for another app on this PC option supply the directory path to the folder where Microsoft Mail is installed. Now all that is left is to confirm your choice by selecting Always use this app to open MMF files and clicking OK.

Change the default application in Mac OS

• Right-click the MMF file and select Information
• Open the Open with section by clicking its name
• Select the appropriate software and save your settings by clicking Change all
• If you followed the previous steps a message should appear: This change will be applied to all files with MMF extension. Next, click the Continue button to finalize the process.

Step 4. Ensure that the MMF file is complete and free of errors

Should the problem still occur after following steps 1-3, check if the MMF file is valid. Problems with opening the file may arise due to various reasons.

1. Check the MMF file for viruses or malware

Should it happed that the MMF is infected with a virus, this may be that cause that prevents you from accessing it. It is advised to scan the system for viruses and malware as soon as possible or use an online antivirus scanner. MMF file is infected with malware? Follow the steps suggested by your antivirus software.

2. Ensure the file with MMF extension is complete and error-free

Did you receive the MMF file in question from a different person? Ask him/her to send it one more time. It is possible that the file has not been properly copied to a data storage and is incomplete and therefore cannot be opened. When downloading the file with MMF extension from the internet an error may occurred resulting in incomplete file. Try downloading the file again.

3. Ensure that you have appropriate access rights

Sometimes in order to access files user need to have administrative privileges. Switch to an account that has required privileges and try opening the Microsoft Mail Message Format file again.

4. Make sure that the system has sufficient resources to run Microsoft Mail

If the systems has insufficient resources to open MMF files, try closing all currently running applications and try again.

5. Ensure that you have the latest drivers and system updates and patches installed

Regularly updated system, drivers, and programs keep your computer secure. This may also prevent problems with Microsoft Mail Message Format files. Outdated drivers or software may have caused the inability to use a peripheral device needed to handle MMF files.

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