How to Deal With Oversized MBOX File Issue

MBOX file is used by many email clients, including Apple Mail, WebMail, PocoMail, Gmail, Postbox, Entourage, Eudora, Opera, Netscape, Thunderbird, etc., to save mailbox data. Just like any other file format, MBOX also faces a lot of issues that need to be addressed. However, with continuous usage, it can become large and cause performance issues when performing email operations. For instance, when the size of MBOX increases, you need to reduce its size.

There are multiple issues that users may face while working with MBOX files, such as errors when opening a file, platform incompatibility, corruption of files, etc.  So, let’s learn how to deal with oversized MBOX file issues to maintain smooth email operations.

Common Solutions to Deal with MBOX Oversizing

Dealing with oversized MBOX files can be a difficult task. However, there are two solutions you can use to reduce the size of MBOX files:

Solution 1: Delete Unnecessary Emails and Compact Folders

It is the first step anyone could think of to create some free space. Look over your mailbox to find out the emails that are not required, and delete them. However, in many MBOX email clients, the folders need to be compacted so as to reclaim the space created by the deletion of items as this is not done automatically. To compact MBOX file size, or folder size, go through the assistance below:

• If you’re using Thunderbird, right-click your mail folder in the left sidebar and select Compact. However, you can also export each folder in a separate MBOX file via ImportExportTools NG add-on.
• If you’re using Apple Mail, use the Mailbox>Export Mailbox feature or rebuild/compact local caches to clear redundant space.

Solution 2: Split MBOX File using a Text Editor

Splitting your MBOX files using a text editor could be a great way to reduce mailbox size. You can use any text editor, including Notepad++, JujuEdit, EditPad Pro, EditPad Lite, EmEditor, HiEditor, HxD, ifhex, HexFiend, UltraEdit, VEDIT, VEDIT Pro64, and Vim for this. Make sure you check the platform compatibility to run these editors on your system. Once you have installed the text editor of your choice, follow the given order of steps:

1. Create two extra copies of the mbox file.
2. Open one of those copies with the text editor.
3. Click anywhere in the middle of the file. Search for the header named Message-ID. It contains a unique value for every mail.

   Note: You can copy that ID separately to Notepad or Notes for reference. Scroll to the end of the message. Delete the entire message below that point and save the file.

4. Open the other copy of your file. Find the unique Message ID from where you split MBOX file.
5. Then, delete all the messages above that Message ID and save it.

Suggestion: Convert and Save Large MBOX file to Multiple Smaller Outlook PSTs

If you’re not satisfied with the above methods or looking for an automated solution, then it is ideal to convert MBOX file into PST format and then split it into multiple files. Kernel MBOX to PST Converter can be a handy utility that will allow you to convert all your MBOX files into PST format and save them into multiple files based on your requirements.

After converting and splitting the MBOX file to PST format, you can easily open the PST file with any version of MS Outlook to access its data. This is the best solution that works for reducing MBOX file size.

Conclusion

MBOX users can choose different ways to reduce the size of their MBOX files. As the first method, they can delete the unwanted emails and then compact the folders. Alternatively, they can split the MBOX file manually using a text editor. And if none of the above methods work for you, then it would be a great option to convert an MBOX file to multiple smaller PST files; you can access them later in Outlook or Microsoft 365.

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