How to Bulk Convert Thunderbird to Maildir File Format?
Published: October 10th, 2025 • 8 Min Read
Overview: In this blog, we will be covering the methods to convert Thunderbird to Maildir. This will cover everything users want to know about the methods, reasons, and challenges they face during the process of conversion process.
- Thunderbird: Thunderbird is a free-to-use email client developed by Mozilla. Thunderbird is a desktop-based email client; this means that data is saved on the system itself. We can integrate different accounts into Thunderbird using IMAP, POP3, and SMTP server settings.
- Maildir: Maildir is a storage format used to store each email message separately. This separately saved format reduced the risk of getting corrupted. Additionally, the backups become easy as all the messages are separated.
The blog provides briefs about the manual method as well as the professional method. These can help users convert Thunderbird to Maildir format.
Why Users Want to Convert Thunderbird to Maildir?
There are multiple situations or conditions that make a user convert Thunderbird to maildir format. However, some of the most prominent causes for the same are as follows:
- Enhanced data safety: The maildir format is more secure because the data files are stored separately; if any file gets corrupted, other files will remain safe.
- Large file handling: The format is able to handle large files easily in clients due to the separation of files; the data can be moved, deleted, and changed easily due to the separation of all files. In contrast, mbox files are required to be rewritten as a whole because they store all the data in a single file.
- Easier backup and sync: Backup and syncing individual files becomes faster and easier as all the files are stored separately. Any individual message can be backed up or synced easily.
- Storage optimisation: When we delete a message in maildir format, the data will be deleted in one and for all copy or entries is saved. In contrast, when we delete or move a data file in a MBOX file, the data entry of the deleted data remainswhich can accumulate over time, making the system heavy.
Thunderbird Export to Maildir Format Manually
The quick and conventional way to convert Thunderbird to Maildir is not so reliable due to its multiple restrictions. However, have a quick look at them to learn the indirect yet free way to export Thunderbird emails to Maildir.
- Firstly, open Thunderbird on your device.
- Now, click on the menu icon >>>Settings >>>General tab.
- Next, scroll down and select “Config editor”.
- Further, click on Show All and search for “mail.serverDefaultStoreContractID”.
- Once found, double-click on it to change the value to“@mozilla.org/msgstore/maildirstore;1”.
- After this, restart Thunderbird and again click on the Menu icon.
- Now, choose Account Settings >>>>Server Settings” from the left panel.
- Then, scroll down and make sure that Maildir is chosen as the storage option.
- Once done, open an email account that is old and has MBOX files.
- Click on any of the emails, drag and drop them to the maildir folder.
- Further, download the ImportExportTools NG plugin on Thunderbird.
- After this, export that email as an EML file.
- Finally, import EML files into an account that is Maildir-based.
Limitation: The method has a high chance of failing as the method is very complex and complicated to follow, even for someone with fair knowledge of people.
Why the Conventional Solution is Unreliable?
- High risk of failure: There is a high chance the method will be unsuccessful or prone to failure. Due to the complexity and technical knowledge required to follow the procedure.
- Complex to use: The manual method to convert Thunderbird to Maildir is very complex and confusing.
- Time-consuming: It is lengthy and thus consumes a lot of user time, effort, and energy. Most users will be unable to follow the procedure with 100% accuracy.
- Inaccuracy in data: The drag-and-drop step of the manual method to convert Thunderbird to maildir may not maintain the data authenticity in terms of formatting.
Most Effective Way to Convert Thunderbird to Maildir
The manual method for Thunderbird export to Maildir is very complicated and has various restrictions that hamper user productivity and data security. Therefore, to reliably do the Thunderbird export to Maildir, professionals always use and recommend an automated tool such as BitRecover Thunderbird Converter solution. It is easy, quick, and trustworthy to share the crucial information and export Thunderbird bulk emails in maildir format effortlessly. The quick steps to use this solution are as follows:
How to Professionally Convert Thunderbird to Maildir?
- Install and run the solution on your device.
- Now, select the Thunderbird data using the given selection modes.
- From the list of 30+ saving modes, choose Maildir.
- Then, give the saving location and choose a naming format.
- Finally, click on Convert to process the Thunderbird to Maildir conversion.
Professional assistance: If you have any queries related to the tool, you can opt for our migration service. This service will include an in-house team that will convert all your Thunderbird data to Maildir for you. The entire process comes with a certificate as proof of successful migration. Additional customised features for the tool are also available on request.
Benefits of Using the Professional Tool
- Bulk Migration: The tool is capable of handling multiple data files, meaning the user can convert multiple files using the select folder option. Additionally is there is no size restriction to the mbox files that need to be imported.
- Easy-to-understand UI: The tool’s User interface is easy to understand and doesn’t require going through a guide. Additionally, this reduces human errors.
- Export with Attachment: The data converted will have all the attachments, like photos, documents, attached to the conversion. Additionally, the metadata, like CC, sender’s name, etc., is also maintained.
- Advance filter option: The tool has an advanced filter, which helps users segregate a specific type of data or individual files. This helps users target only the required data.
- Time-saving: The tool’s automated approach and capabilities help the user save time and effort.
FAQ: Frequently Asked Questions
Q1: What is the format in which Thunderbird exports data files?
Ans. The main format in which Thunderbird saves its data in the local system is .mbox or MBOX. This is a single-file-based storage format. This means that all the data is saved in a file MBOX file. This MBOX is required to import data.
Q2: Why is Maildir better than the MBOX format?
Ans. Although Maildir is a good format, in some cases better than MBOX, but which is better is still a debate topic.
MBOX saves all data in a single data file, which means any change will require the email client to rewrite the entire file.
whereas Maildir is saved individually, which makes it faster to sync, move, and remove individual messages
Q3: Can Thunderbird read Maildir format?
Ans. Thunderbird can read the Maildir format to some extent, as Thunderbird 38 has an experimental feature for Maildir; therefore, we can use Maildir in Thunderbird, but be prepared for risks like data loss, corruption, etc. If you have maildir data, it’s better to convert that into mbox files first.
Q4: Difference between the maildir and mbox formats?
Ans. The main difference is the style of storage structure. Maildir has a separate-based email structure, meaning the data messages are stored on an individual basis, but in MBOX, all conversion data is stored in a singular file.
Conclusion
In this blog post, we briefly highlighted the best way to convert Thunderbird to Maildir format. However, we came to know that the conventional way has lots of limitations, and that is why experts always suggest using an automated solution like the one mentioned above. Therefore, the professional solution is very compatible as it runs on all devices and their editions, including Windows and Mac OS. Hence, it is the best alternative for Thunderbird export to Maildir due to its ease of use and data authenticity features.
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