# Cyrus IMAP Server: Alternate Namespace

This document describes the alternatives to the standard mailbox presentation method. These alternatives may be used together or independently.

The namespace options do NOT change the rules governing the behavior of mailboxes (as described in overview.html) or how mailboxes are stored on the filesystem. The mailboxes are ALWAYS stored using the `netnews` convention and internal namespace. When configured to use one (or both) of the options below, the server simply translates mailbox names between the internal names and the external names when used by the client in the IMAP protocol and in Sieve scripts.

This design allows the namespace to be changed at runtime (even on a running server) without having to reconfigure the server. This also means that one mailstore can support multiple namespaces if configured correctly.

NOTE: If you are upgrading an existing server which uses `timsieved` to manage Sieve scripts and choose to enable one of the namespace options, you should run the script "`tools/translatesieve`" after configuring the namespace option(s). This script will translate the folder names in `fileinto` actions.

## Alternate Mailbox Namespace

The alternate namespace allows a user's personal mailboxes to appear as if they reside at the same level as that user's `INBOX` as opposed to children of it. For example, if user "`bovik`" had a personal "`work`" mailbox, it would appear to user "`bovik`" as "`work`" instead of "`INBOX.work`" as it would in the standard namespace.

This configuration requires that a special prefix be used for shared folders (to distinguish them from personal folders) and for accessing other users' folders. By default, the prefix for shared folders is "`Shared Folders`" and the prefix for other users folders is "`Other Users`". For example, a shared folder "`foo`" in the standard namespace would be presented as "`Shared Folders.foo`" in the alternate namespace.

NOTE: All tools for administering the server, including admins using cyradm, always use the internal namespace.

### Configuring the Alternate Namespace

To use the alternate namespace, turn on the `altnamespace` option in `/etc/imapd.conf`. The prefixes used for shared folders and other users folders can be changed from the defaults by setting the `sharedprefix` and `userprefix` options respectively.

## UNIX Hierarchy Convention

The UNIX hierarchy convention uses the traditional UNIX separator character ("/") to delimit levels of the mailbox hierarchy instead of the `netnews` character ("."). For example, if user "`bovik`" had a personal "`work`" mailbox, it would appear to user "`bovik`" as "`INBOX/work`" in the standard namespace.

When the UNIX hierarchy convention is used, the "." character MAY be used in mailbox names, including user names. In order to maintain backwards compatibility with the internal namespace, all "." characters are translated to a benign character (currently "^") before any data is stored to disk. For example, if user "`elmer.fudd`" had a personal "`rabbit.holes`" mailbox, it would be stored as "`user.elmer^fud.rabbit^holes`" in the internal namespace. It is important to remember this phenomenon if/when reverting back to the `netnews` hierarchy convention.

### Configuring the UNIX Hierarchy Convention

To use the UNIX hierarchy separator, turn on the `unixhierarchysep` option in `/etc/imapd.conf`.

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