[Fixed] “Messaging Interface has Caused an Unknown Error” in Outlook

Summary: In this guide, you will learn the different techniques to resolve “the messaging interface has returned an unknown error” in MS Outlook.

User Query:

When I opened my Outlook account to create a new email message. I encounter an error message stated: “The messaging interface has returned an unknown error. If the problem persists, restart Outlook.” When I attempted to click the OK button to close the error message, it pops up too.

Most of the forum sites are flooded with these kinds of user queries. If you are also experiencing the same issue then this blog resolve all these problems.

How to Fix “Messaging Interface has Caused an Unknown Error”?

To troubleshoot the messaging interface has returned an unknown error Outlook 2016, 2013, 2010, 2007, 2003, etc, here we have discussed all the possible solutions. Let’s explore each one of them.

Method 1- Use SCANPST.exe

Inbox Repair Tool is an inbuilt Microsoft Tool to deal with fixing the PST corruption issues. It will help to fix this error, if the corrupted PST file is responsible for the “messaging interface has caused an unknown error” this error message.

Let’s look at the steps required to repair file.

1. Close Outlook completely.
2. Now, open the Inbox Repair Tool.
3. Browse the PST file you want to scan or type the location of the PST file.
4. Click on Start button to initiate the scanning process.
5. Press OK when the scan is complete.
6. Now, restart Outlook to check if the items are accessible.

If the PST file is highly corrupted and you are unable to fix the PST corruption issue with this method, then you have to use an automated tool which is known as PST recovery. The software smartly deals with complex corruption and broken problems associated with files. The tool has the ability to recover permanently deleted emails, contacts, calendars & other items. It will help you to fix the Microsoft outlook message interface has returned an unknown error.

Method 2- Create New Outlook PST File

Another way to get rid out of this unknown error is by creating a new PST file in Outlook. And then importing the information from the original PST.

1. Exit Outlook, go to Start >> Settings >> click Control Panel.
2. Double-click Mail, go to Services tab >> Personal Folders >> click Remove.
3. Click Add, go to Available information services box, click Personal Folders and hit OK.
4. Enter the user’s first name, click Open, click OK twice and exit Control Panel.
5. Now, start Outlook to check if the issue is resolved.

If the issue is resolved, you can import data from the Original PST to the newly created Outlook PST. Follow the steps:

1. Go to the File menu >> select Import and Export option.
2. Click Import from a personal folder file (.pst) and hit Next.
3. Now, type the path to the PST file in the File and click Next.
4. Ensure that Personal Folders is selected (as the folder to import from and the folder to import into) and click Finish.

Method 3- Create a New Outlook Profile

Sometimes creating a new profile in an Outlook account helps in resolving the “Microsoft outlook message interface has returned an unknown error”.

Follow the below-mentioned steps to create a new Outlook profile:

1. Exit the Outlook application.
2. Go to Start >> Settings >> click Control Panel.
3. Double-click Mail, click Show Profiles >> click Add.
4. Select the services you need and click Next.
5. Provide necessary information related to the selected services on Inbox Setup Wizard.
6. Type new and click Next, when prompted to enter the path to PST files and complete the steps in Inbox Setup Wizard.
7. Go to the General tab, when you start Microsoft Windows Messaging, select the newly created profile and click Close.
8. Open Outlook and start working as usual.

Method 4 – Install New MAPI files

Messaging Application Programming Interface (MAPI) for Outlook is an API that lets users to access their mailbox. MAPI library files are stored in the supported versions of the Windows system under the below path:

/Windows/System32/mapi32.dll

or

/Windows/syswow64/mapi32.dll.

The information related to MAPI installation can be found in the registry editor under below path:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Messaging Subsystem.

To fix the messaging interface has returned an unknown error issue, you need to follow the below-mentioned steps:

1: First close Outlook applications.

2: Now, go to the registry editor path –
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Messaging Subsystem.

3: Next, move the mapi32.dll file to another location from the existing location.

/Windows/System32/mapi32.dll

or

/Windows/syswow64/mapi32.dll.

4: Go to the Microsoft website and download the latest mapi32.dll file compatible with your Outlook version and paste it in the location in the above step.

5: At last restart your Windows and then open Outlook.

So, far you have learned the all the manual workarounds to fix the “Outlook the messaging interface has returned an unknown error”.

Final Verdict

Microsoft Outlook interface has caused an unknown error is one frequently getting errors. It will turn and lead to several impacts on the Outlook PST file, if not resolved immediately. So, in this article, we have mentioned some manual workarounds to resolve the messaging interface has returned an unknown error Outlook 2016 and below versions.

However, if the issue still persists in their Outlook account then users can opt for the third-party tool. The tool discussed above efficiently repairs the severely corrupted, large-sized, and encrypted PST data files within a few single clicks.