What is Maildir Format? - Know Maildir and Maildir++ Differences

Emails are saved in a database file saved locally on a Windows PC. These allow access to mailbox data even when not connected to the internet. It is the most common method of saving messages opted by many leading email clients. This post talks about one such file format and explains all that there is about what is Maildir file format. It provides a detailed introduction and what it is all about. This Maildir file extension contains all the relevant information about the topic. It is very useful for entrepreneurs and non-technical businessmen not familiar with the file type.

In order to read such files, SysTools developed an advanced Maildir File Viewer to preview data with each sub-directory

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What is Maildir & Maildir ++ File: A Brief Introduction

It is an email format which is used for storing messages only. It is a more organized and systematic way of storing mailbox data. It was introduced by Qmail client and is used by many other applications like Mozilla Thunderbird. It creates a separate file with a unique name for each incoming message.

One Such Extension to Maildir was found, named as Maildir++ which aimed at supporting mail quotas & sub-folders. The Sub-directories within Maildir++ files start with (dot) "." (eg, " .Inbox ", ".Drafts " etc.). This Maildir++ files follows the same specification as that of Maildir

Maildir++ file Extension

Key Differences Between Maildir and Maildir++ Files

The below listed table provides a concise overview of the key differences between Maildir and Maildir++ files. Highlighting their respective features and suitability for different use cases.

Features	Maildir	Maildir++
Subfolder Support	Does not support subfolders.	Supports subfolders, allowing for hierarchical folder structures.
Quota Management	Does not include built-in quota management features.	Includes quota management capabilities for controlling storage usage.
Scalability	Highly scalable for basic email storage needs.	Suitable for larger organizations or service providers with extensive storage requirements.
Compatibility	Widely compatible with email clients and systems.	Maintains backward compatibility with Maildir while offering additional features.
Maintenance	Relatively simple to maintain and manage.	Requires additional configuration and management for quota and subfolder support.
Usage	Suitable for basic email storage and retrieval.	Ideal for environments requiring detailed folder structures and quota management.

Quick Glance at Maildir File Structure

After Knowing about What is Maildir. Lets know about Maildir Directory Structure. This file type organises each folder in a new directory. The most important ones are discussed below:

Tmp: It stores the emails temporarily for the current mailbox.
New: Each incoming message is saved in this sub-directory (which is unread). It saves the meta properties of emails including ‘Return-path’ and ‘Delivered-To’ details. This information can be crucial in forensic analysis and for tracing the route or path taken by the email. The Maildir file extension receives messages in RFC 822 format. It keeps the text integrity intact. This directory also keeps a record of creation date and any last modifications or edits made.
Cur: It saves all the messages that have already been read. This indicates the very organized structure of the Maildir file format. It creates a separate folder for keeping the opened messages. It helps investigators to examine a cybercrime by scanning only part of the database.

maildir vs maildir++

The above image displays a pictorial representation of how a typical client stores data using Maildir file format. The structure defines a home directory that branches into a separate folder for each user. One can browse to different sub-directories created for each account to read emails corresponding to that particular mailbox.

Maildir File Naming Convention

This section will describe about basic file naming Convention of Mialdir file format.Generally, Maildir file is seen as a file as:

File Naming Notation : <basefilename > , < filesize >, < flag>

1464003587.H805375P95754.gator3018
.hostgator.com,S=20238_2,S

naming Convention of maildir and maildir++

File Name	Description
1464003587.H805375P95754.gator3018.hostgator.com, S=20238_2, S	Denotes Arrival Timestamp
1464003587.H805375P95754.gator3018.hostgator.com, S=20238_2, S	Specifies the size of email message
1464003587.H805375P95754.gator3018.hostgator.com, S=20238_2, S ( or R , F)	(Seen)S : Specifies that user has successfully viewed email message but not read them (Read)R : Specifies taht user has successfully read email message (Flagged)F : Specifies that user has flagged hat particular message

Benefits of Maildir File Format

Here are some of the advantages of using this Maildir Directory Structure in any emailing application:

It is a secure file format and has minimal chances of corruption or damage.
It can be used over a network file system without any kind of compatibility issues. It is easier to share and access across platforms or systems.
Maildir file extension has a great message filtration system. Incoming text is directly sent to appropriate subfolder.
It allows for faster access to emails because of its unique structure. It can be beneficial in forensic analysis of a data file and to detect a possible cybercrime.
It makes for faster searches, retrieval, deletion of emails from a Maildir file.

Maildir File Extension Compatibility

Here are some of the examples of where this file format is used:

Mail Servers: Qmail, Xmail, Exim, Dovecot, Courier Mail Server
Email Clients: Thunderbird(Beta), Pine, Malix, Mutt, Alpine, Balsa, Cone
Delivery Agents: Procmail, Maildrop, Getmail, MSwatch, MPOP

Make Maildir and Maildir++ Accessible in Other Platforms

Having Maildir and Maildir++ restrct users to access the data. To overcome this limitation SysTools developed an advanced and all-in-one Maildir Converter Tool. it allows uses to export complete data from Maildir and Maildir++ files and make it compatible with other platforms.

Steps to Use This Software