Automatic Creation of Mailboxes

Cyrus IMAP features the ability to create mailboxes automatically;

  • for successful login events,

  • for email messages that arrive for a user,

  • when a Sieve script uses the "fileinto" action.

When operating an IT infrastructure, Cyrus IMAP may only be one part of such larger environment. When adding a user John Doe <>, several pieces may need to fall or put in place to ensure the account is fully functional.

Cyrus IMAP allows the automatic creation of John's INBOX, and selected sub-folders, either when John first logs in to Cyrus IMAP, or when the first message is to be delivered to John's INBOX.

Additional features of this functionality include;

  • the automatic creation of a Sieve script for Server Side Filtering (Sieve).

  • setting a storage quota and message quota for the user,

  • automatic subscription to folders in the Personal Namespace,

  • automatic subscription to a selection of or all shared folders.


Third party solutions incorporating Cyrus IMAP, and distributors of Cyrus IMAP (such as your Linux distribution) may have disabled this functionality altogether, during the building of the packages -- most likely because they employ different means to get user's mailboxes created.

Cyrus IMAP does not currently strip options from man-pages that are rendered irrelevant by the functionality not being built in, so while the man-page on your system may refer to settings related to this functionality, the actual functionality may not be available.

To enable the automatic creation of mailboxes, set the following options in imapd.conf(5).

autocreate_quota: -1

If set to a value of zero or higher, users have their INBOX folders created upon a successful login event or upon lmtpd(8) message delivery if autocreate_post is enabled, provided their INBOX did not yet already exist.

The user's quota is set to the value if it is greater than zero, otherwise the user has unlimited quota.

Note that quota has kibibyte granularity. Values specified here will be truncated to the nearest whole kibibyte.

For backward compatibility, if no unit is specified, kibibytes is assumed.

autocreate_post: 0

If enabled, when lmtpd(8) receives an incoming mail for an INBOX that does not exist, then the INBOX is automatically created by lmtpd(8) and delivery of the message continues.

Other settings in imapd.conf(5) affecting automatic options.

Autocreation of mailboxes

autocreate_inbox_folders: <none>

If a user does not have an INBOX already, and the INBOX is to be created, create the list of folders in this setting as well. autocreate_inbox_folders is a list of INBOX's subfolders separated by a "|", that are automatically created by the server under the following two scenarios. Leading and trailing whitespace is stripped, so "Junk | Trash" results in two folders: "Junk" and "Trash". See also the xlist-flag option, for setting special-use flags on autocreated folders.

INBOX folders are created under both the following conditions:

  1. The user logins via the IMAP or the POP3 protocol. autocreate_quota option must have a value of zero or greater.

  2. A message arrives for the user through the lmtpd(8). autocreate_post option must be enabled.

Automatic quota settings

autocreate_quota_messages: -1

If set to a value of zero or higher, users who have their INBOX folders created upon a successful login event (see autocreate_quota), or upon lmtpd(8) message delivery if autocreate_post is enabled, receive the message quota configured in this option.

The default of -1 disables assigning message quota.

For consistency with autocreate_quota, a value of zero is treated as unlimited message quota, rather than a message quota of zero.

Autocreation of Sieve scripts

autocreate_sieve_folders: <none>

A "|" separated list of subfolders of INBOX that will be automatically created, if requested by a sieve filter, through the "fileinto" action. The default is to create no folders automatically.

Leading and trailing whitespace is stripped from each folder, so a setting of "Junk | Trash" will create two folders: "Junk" and "Trash".

autocreate_sieve_script: <none>

The full path of a file that contains a sieve script. This script automatically becomes a user's initial default sieve filter script.

When this option is not defined, no default sieve filter is created. The file must be readable by the Cyrus daemon.

autocreate_sieve_script_compile: 0

If set to yes and no compiled sieve script file exists, the sieve script which is compiled on the fly will be saved in the file name that autocreate_sieve_compiledscript option points to. In order a compiled script to be generated, autocreate_sieve_script and autocreate_sieve_compiledscript must have valid values

autocreate_sieve_script_compiled: <none>

The full path of a file that contains a compiled in bytecode sieve script. This script automatically becomes a user's initial default sieve filter script. If this option is not specified, or the filename doesn't exist then the script defined by autocreate_sieve_script is compiled on the fly and installed as the user's default sieve script

Automated folder subscriptions

autocreate_subscribe_folders: <none>

A list of folder names, separated by "|", that the users get automatically subscribed to, when their INBOX is created. These folder names must have been included in the autocreateinboxfolders option of the imapd.conf.

autocreate_subscribe_sharedfolders: <none>

A list of shared folders (bulletin boards), separated by "|", that the users get automatically subscribed to, after their INBOX is created. The shared folder must have been created and the user must have the required permissions to get subscribed to it. Otherwise, subscribing to the shared folder fails.

autocreate_subscribe_sharedfolders_all: 0

If set to yes, the user is automatically subscribed to all shared folders, one has permission to subscribe to.

Autocreation of users

autocreate_users: anyone

A space separated list of users and/or groups that are allowed their INBOX to be automatically created.

See imapd.conf(5) for the full documentation of all options.

Limitations to the Automatic Creation of Mailboxes

  1. A user may in fact be able to successfully login to IMAP with both a full primary recipient email address such as, as well as a secondary recipient email address such as

    Unless a process known as login username canonification is used, this could result in two different mailbox hierarchies being created;

    • user/

    • user/

  2. When a user Jane Gi <> marries John Doe and adopts her new husband's surname, her primary recipient email address may change to become

    Note that John Doe does not need to be an user for such event to occur, and that many countries allow the husband to take the maiden name of their spouse instead -- so even if the employees and/or associates of an organization running Cyrus IMAP are exclusively male, this may still apply to that organization.

    The functionality stated in this document does not rename user/ to become user/

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