How to fix “no valid MBOX files were found” Error

Are you facing error “no valid MBOX files were found” or “Mailbox is Not a Valid MBOX File”?; Do you want to know a quick trick to rectify this problem?

Then you are in the right place. Here, in this blog, we are going to discuss how to fix error syncing inbox failed mailbox isn’t a valid MBOX file by the alternative method.


In today’s world emails is the major form of cross-communication among Enterprises. So there is a very high demand for good professional email clients in the market. That’s why so many different email clients are also coming into existence and they have their own, different format for storing email data. Among many of the emails clients, one of them is MBOX which is used on the various operating system.

About MBOX Mailbox

MBOX is a generic term for a group of related file formats used for holding collections of email messages. It is one of the most popular file formats to save electronic mail messages. MBOX file format is used by various email clients like Thunderbird, AppleMail, Entourage, Mulberry, Eudora, SeaMonkey, Pocomail, Spicebird, Netscape, Gnu Mail, Sylpheed, ClawsMail, OperaMail etc. Unfortunately, there are times when a user has to face an MBOX error due to some MBOX file corruption situation. Few of them are:

Causes of Mailbox is not a valid MBOX file

Most of the user face an error no valid MBOX files were found when they try to import MBOX files. MBOX is a versatile file format that is been used by many different clients according to their business community. There are some reasons that cause this error like

When a user is trying to access an inappropriate directory means if a Mac OS user is trying to import an MBOX file from a different version of Mac OS, due to incompatibility user will face an error.

Another reason is that user is trying to import corrupted MBOX file.

How to Fix No Valid MBOX files were Found

To help you understand easily let’s take a situation where a user is trying to copy an old MBOX file to the external drive. After you try to import one file at a time into the mail, unfortunately, every time a dialog box encountered, which say “no valid MBOX files were found”.  Now, the question arises is how should we import MBOX file into the mail?

These are the steps you need to follow to import MBOX files:

Step.1: Quit Apple Mail.
Step.2: Select the location of the mailbox folders that you want to import.
Step.3: In the selected folder you will find a root folder for every account that you have added to Apple Mail. Now navigate down and go to the main root mailbox folder for directory hierarchy. Open the located .mbox file and find the mailbox folder which you want to restore.
Step.4: After identifying the file you want to recover, open Apple Mail and click on File/import mailboxes.
Step.5: After few seconds a wizard will open that will guide you the whole procedure.
Step.6: Now locate the Mbox files to you have recovered.

A confirmation screen will appear, showing the process was successful in importing the files and are located in the imported folder. The mailbox imported will be the duplicate of the folder from Mbox folder or external backup Mbox files. After all this, a new window will pop up providing where about the imported files.

You may also like to read: Recover deleted Apple Mail Emails

Alternative Method to Fix no valid MBOX files were found Error

Manual procedure is suited for importing small mailbox folders only because when you trying to import years of email it becomes very complex. It would be very time consuming and not effective, to avoid this hectic process you can use any third party Mbox file recovery software. In fact, there are tons of software in the market that will not only recover/repair but also convert them to any file format that you need like MBOX to PST, MBOX to NSF, MBOX to MSG etc.

With the help of free MBOX to PST Converter software online, it becomes very easy to repair damaged or corrupt MBOX file. Once the file is recovered, you will nor get the error i.e. “Mailbox is not a valid MBOX file.” The tool brings you with various other feature to convert multiple MBOX files into PST easy and quick. It is compatible with all versions of Windows Operating System.

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