How to Split Large MBOX Files of Google Takeout

Exporting all years of your emails from Gmail using Google Takeout is a must-have process for creating backups; however, it results in huge archives. Opening and importing such files into desktop clients for email, like Mozilla Thunderbird, Apple Mail, and Microsoft Outlook causes hanging of applications or even crashing of your computer. The solution is obvious: you have to split large MBOX files of Google Takeout exports.   In this ultimate guide, we will explain to you why Splitting Oversized Email Archives is required and ways to split large MBOX Files Google Takeout produces.

Why Do You Need to Split Large MBOX Files of Google Takeout?

The Google Takeout utility will save your Gmail mailbox in the form of one huge MBOX file called All mail including Spam and Trash .mbox. Your files may grow to 20 GB, 50 GB, or even higher.   

The following problems arise when dealing with very big MBOX files: 

• Usually desktop email clients cannot work with files bigger than 10-20 GB.
• Migration software and web mail importers frequently timeout while working with huge archives.
• Reading very big files requires a lot of RAM memory. Freezing of your computer during reading may lead to corruption of the whole archive. Limited Search Possibilities: Searching for one message in 40 GB of MBOX is a rather memory-consuming process.

Method 1: Break Down Big MBOX Files Created From Google Takeout Through Thunderbird for Free

If you want to use a totally free process, there’s no better solution than Mozilla Thunderbird with the ImportExportTools NG extension. Here you have the ability to break down your archive by years, months or folders while retaining all the metadata and attachments.

Step 1: Installation of Thunderbird and ImportExportTools NG Install Thunderbird on your PC from Windows, Mac, or Linux.    

• Launch Thunderbird. If a prompt comes up asking you to set up a mail account, then just ignore it because you do not need one at all.   
• Click on Tools/Menu > Add-ons and Themes.  
• Type in "ImportExportTools NG" and add it to Thunderbird.

Step 2: Import the Google Takeout MBOX File Unzip the Google Takeout zip download file to get to the .mbox file.   

• Right click on Local Folders in the navigation pane on the left side of Thunderbird.  
• Go to ImportExportTools NG > Import mbox file > Individual mbox files.   
• Find your .mbox file in the Takeout directory that you unzipped and select it.

Step 3: Creating Subfolders and Splitting Emails Data

• Right-click Local Folders and create subfolders for respective years or other categories  like Mail_2024, Mail_2025.   
• Right-click your imported main folder to see the list of emails. 
• Arrange the emails according to Date.   
• Select some emails like 2024 emails, right-click, and choose Move To > Local Folders > Mail_2024.

Step 4: Export the Smaller MBOX Files 

• Right click on the new folder like Mail_2024.  
• Go to Import/ExportTools NG > Folder Export .mbox > As mbox File.  
• Select the location on your computer where you want to save the smaller MBOX file.
• Using this approach, you will be able to split large MBOX files that are generated through Google Takeout.

How to Split Large MBOX Files of Google Takeout Using Professional Software? 

One of the most reliable methods of dividing the huge emails from Google Takeout is using SysTools MBOX Splitter Tool. Since all the emails that have been backed up from Gmail via Google Takeout are dumped into a single .mbox file (ranging from 20 GB to more than 50 GB), opening or importing such huge files into applications like Thunderbird, Apple Mail, and Outlook causes application freeze and data loss.

Google Takeout Archive Key Splitting Variants

• Splitting Based on Desired File Size: It is possible to select the desired file size between 1 MB and 20 GB. It means that you can split a 50 GB Google Takeout MBOX file to get separate 2 GB or 5 GB archives. 
• Splitting Based on a Date or Date Range: Define the starting and ending dates to filter out emails sent in certain time periods. 
• Splitting Based on Year: The single large Takeout file will be split into different MBOX files according to the selected years. 
• Splitting by Sender or Subject: You can filter or split your archive based on senders' addresses or email subjects.

Step-by-Step: How to Divide Google Takeout Files

• Unpack Takeout archive: Extract your downloaded Google Takeout .zip archive to access the All mail including Spam and Trash .mbox archive.
• Add MBOX File: Launch that professional software MBOX Splitter and click Add File/Folder button to add your Takeout MBOX archive.   
• Set Split Criteria: Set your own criteria to split, such as split by size (for example, choose Split by Size and set 2048 MB for splitting in 2 GB chunks).
• Set Output Directory: Browse for and select the target directory where you would like to save your split MBOX archives. Get Started: Click Split button.

Conclusion

Dividing large MBOX files created through Google Takeout is vital in order not to suffer from possible computer slowness, application crashes, or file damage, because typical desktop e-mail clients tend to hang while trying to import one archive bigger than 10-20 GB. It is important to divide your backup into smaller boundary-compatible pieces so that your emails could stay completely readable, whole, and transferable. According to your level of skillfulness, availability of time, and funds, you have different options to do so either by free manual way using Mozilla Thunderbird software along with ImportExportTools NG extension in order to manually arrange mails in smaller folders, or with help of boundary aware Python script which will automatically cut your archive into pieces of certain size, for instance 2 GB pieces, or by using special paid programs such as professional tools are capable of dividing multi-gigabyte files either by size, date or by year. By employing one of the above methods with the copy of your initial archive, you will be able to safely process it further.

FAQ

Q1. Why does Apple Mail stop working or crash while importing Google Takeout files as MBOX format?

Because Apple Mail works to parse and index imported files into its SQLite database at the same time. When the imported file is bigger than 10GB, it will use up all available RAM.

Q2. Is there any chance that splitting my MBOX file will affect the original one which I exported from Google Takeout?

No. The split scripts and conversion tools read your original .mbox file and create new smaller .mbox files in a different directory location.