Maildir (run by Courier IMAP or Dovecot) is a mail format used in conjunction with an MTA to store email on the server as separate files within folders.  This post covers Courier IMAP as a service, not in terms of mail client usage.

Directory Structure

A user’s email is store in ”’/home/user/mail/<domain>/<emailuser>/…”’. Below is a sample directory structure of an email account:

• /home/username/mail (mail folder)

  • /domain.com (domain)

  • admin (email user)

  • maildirsize (quota/usage summary, expendable)

  • cur (default inbox for read email)

  • new (default email for unread email)

  • Drafts ( sample folder )

    • - cur (read email)

    • - new (unread email)

• /home/username/etc

  • /domain.com (domain)

    • passwd (contains email account list and UIDs, similar to /etc/passwd)

    • shadow (contains email passwords, similar to /etc/shadow)

    • quota (contains email account quota info)

Folders

So basically, each email user has its own folder, each containing the main inbox (cur/new), and separate email folders. Each separate inbox folder also contains a ”’cur”’ and ”’new”’ folder.

• cur – read email

• new – unread email

Email that is marked as read by the IMAP client (outlook, etc) is moved from ‘new’ to ‘cur’ .

Etc Files

Here’s a sample passwd file:

admin:x:510:510::/home/vnessa5/mail/v-nessa.net/admin:/bin/bash
support:x:513:513::/home/vnessa5/mail/v-nessa.net/support:/bin/bash

Similar to the /etc/password on the server, the file contains some critical pieces of information. From left to right:

• username
• password (x indicates the password is in a shadow file)
• UID (should match main user’s UID in /etc/password)
• GID (should match main user’s GID in /etc/password)
• home folder (location of the email account’s mail folders)
• shell (not relevant)

Permissions

There is a script in cPanel to attempt to fix user mail permissions, which is safe to run on a VPS or Dedicated server, but should not be run on shared without approval from a system admin:

/scripts/mailperm

The permissions should be as follows:

- /home/user/etc (user:mail, 755)
- domain.com (user:mail, 770)
- passwd (user:mail, 644)
- shadow (user:mail, 644)

The other permissions can be 755 user:user, as those files don’t affect email delivery.

The ‘fixperms’ command on the shared servers should fix the permissions of a user’s home folder, including mail and etc.

Converting to Maildir

/scripts/convert2maildir

This will leave the inbox files behind if you’re coming from Mbox, so you can list/remove them with:

find /home/*/mail/* -name inbox -exec ls -la {} \;

Related posts:

• Quota Errors in Exim’s Panic Log
• Fatal! Write failure for /etc/valiases/..
• The cPanel Backup System
• Localdomains vs. Remotedomains
• Simple Bash Script to Fix Account Permissions