Imapc Mailbox Format

The imapc storage accesses a remote IMAP server as if it were a regular (local)
Dovecot mailbox format. Dovecot can treat it as a dummy storage or optionally a
more capable storage.

For information on how to configure imapc in Dovecot, see Imapc Configuration.



imapc-format

=======================================================


Imapc Configuration

See Imapc for a technical description of Dovecot’s imapc mailbox format.



Mail Location Configuration Examples

# In-memory index files:
mail_location = imapc:

# Store index files locally:
mail_location = imapc:~/imapc 



Connection Settings



imapc_cmd_timeout

Default: 5 mins
Values: Time

    How long to wait for a reply to an IMAP command sent to the remote IMAP 
    server before disconnecting and retrying.



imapc_connection_retry_count

Default: 1
Values: Unsigned integer

    How many times to retry connection against a remote IMAP server?



imapc_connection_retry_interval

Default: 1 secs
Values: Millisecond Time

    How long to wait between retries against a remote IMAP server?



imapc_features

Default: 
Values: String

    A space-separated list of features, optimizations, and workarounds that can 
    be enabled.



    Features


    acl
    When this feature is enabled and the imap-acl plugin is loaded, using a
    remote location via imapc will make IMAP ACL commands (MYRIGHTS, GETACL, 
    SETACL, DELETEACL) proxied to the remote.
        New in version 2.3.15.


    delay-login
    Don’t connect to the remote server until some command requires it. By 
    default the server is connected to immediately on login.
        New in version v2.2.29.


    gmail-migration

    Enable GMail-specific migration. Use IMAP X-GM-MSGID as POP3 UIDL. Add 
    $GMailHaveLabels keyword to mails that have X-GM-LABELS except for \Muted 
    keyword (to be used for migrating only archived emails in All Mails). Add 
    pop3_deleted_flag to mails that don’t exist in POP3 server.


     modseq
        Access MODSEQ and HIGHESTMODSEQ
        New in version 2.2.24.


     proxyauth
    Use Sun/Oracle IMAP-server specific PROXYAUTH command to do master user
    authentication. Normally this would be done using the SASL PLAIN 
    authentication.


     throttle:::
    When receiving [THROTTLED] response (from GMail), throttling is applied.

    INIT = initial throttling msecs (default: 50 ms), afterwards each subsequent
    [THROTTLED] doubles the throttling until MAX is reached (default: 16000 ms).
    When [THROTTLED] is not received for a while, it’s shrank again. The initial
    shrinking is done after SHRINK (default: 500 ms). If [THROTTLED] is received
    again within this timeout, it’s doubled, otherwise both throttling and the 
    next shrinking timeout is shrank to 3/4 the previous value.



Optimizations


    fetch-bodystructure

    Allow fetching BODY and BODYSTRUCTURE FETCH BODY.PEEK[HEADER.FIELDS (..)].


     fetch-headers

    Allow fetching specific message headers from remote server.

        New in version 2.2.30.


     rfc822.size 
        Allow passing through message sizes using FETCH RFC822.SIZE.


     search 
        Allow using SEARCH command.



Workarounds


        fetch-fix-broken-mails
    If a FETCH returns NO (but not NO [LIMIT] or NO [SERVERBUG]), assume the 
    mail is broken in server and just treat it as if it were an empty email.

    Warning
    This is often a dangerous option! It’s not safe to assume that NO means a 
    permanent error rather than a temporary error. This feature should be 
    enabled only for specific users who have been determined to be broken.


         fetch-msn-workarounds 
    Try to ignore wrong message sequence numbers in FETCH replies whenever 
    possible, preferring to use the returned UID number instead.


         no-examine 
    Use SELECT instead of EXAMINE even when we don’t want to modify anything in
    the mailbox. This is a Courier-workaround where it didn’t permanently assign
    UIDVALIDITY to an EXAMINEd mailbox, but assigned it for SELECTed mailbox.


         zimbra-workarounds 
    Fetch full message using BODY.PEEK[HEADER] BODY.PEEK[TEXT] instead of just 
    BODY.PEEK[] because the header differs between these two when there are 
    illegal control chars or 8bit chars. This mainly caused problems with dsync,
    but as of v2.2.22+ this should no longer be a problem and there’s probably 
    no need to enable this workaround.



More Config Directives



imapc_host

Default: 
Values: String

    The remote IMAP host to connect to.



imapc_list_prefix

Default: 
Values: String

    Access only mailboxes under this prefix.

    Example, for a source IMAP server that uses an INBOX namespace prefix:

    imapc_list_prefix = INBOX/



imapc_master_user

Default: 
Values: String

    The master username to authenticate as on the remote IMAP host.

    To authenticate as a master user but use a separate login user, the 
    following configuration should be employed, where the credentials are 
    represented by masteruser and masteruser-secret:

    imapc_user = %u
imapc_master_user = masteruser
imapc_password = masteruser-secret

    Mail user variables can be used.

    See also
    imapc_password
    imapc_user



imapc_max_idle_time

Default: 29 mins
Values: Time

    Send a command to the source IMAP server as a keepalive after no other 
    command has been sent for this amount of time.

    Dovecot will send either NOOP or DONE to the source IMAP server.



imapc_max_line_length

Default: 0
Values: Size

    The maximum line length to accept from the remote IMAP server.

    This setting is used to limit maximum memory usage.

    A value of 0 indicates no maximum.



imapc_password

Default: 
Values: String

    The authentication password for the remote IMAP server.

    If using master users, this setting will be the password of the master user.

    See also
    imapc_master_user
    imapc_user



imapc_port

Default: 143
Values: Unsigned integer

    The port on the remote IMAP host to connect to.



imapc_rawlog_dir

Default: 
Values: String

    Log all IMAP traffic input/output to this directory.

    See also
    Rawlog



imapc_sasl_mechanisms

Default: plain
Values: String

    The SASL mechanisms to use for authentication when connection to a remote 
    IMAP server.

    The first one advertised by the remote IMAP sever is used.

    Example:

    imapc_sasl_mechanisms = external plain login



imapc_ssl

Default: no
Values: no, imaps, starttls

    Use TLS to connect to the remote IMAP server.


Value
 Description
no
 No TLS
imaps
 Explicitly connect to remote IMAP port using TLS
starttls
 Use IMAP STARTTLS command to switch to TLS connection



imapc_ssl_verify

Default: yes
Values: Boolean

    Verify remote IMAP TLS certificate?

    Verification may be disabled during testing, but should be enabled during 
    production use.

    Only used if imapc_ssl is enabled.

    See also
    imapc_ssl



imapc_user

Default: 
Values: String

    The user identity to be used for performing a regular IMAP LOGIN to the 
    source IMAP server.

    Mail user variables can be used.

    See also
    imapc_master_user



     imapc_password 



Usage Examples

Do a regular IMAP LOGIN, using STARTTLS, to imap.example.com:

    imapc_host = imap.example.com
imapc_password = secret
imapc_port = 143
imapc_ssl = starttls
imapc_user = user@example.com 



Quota

Using the imapc quota backend allows asking for the quota from remote IMAP 
server (v2.2.30+). By default it uses GETQUOTAROOT INBOX to retrieve the quota.

There are two parameters that can be used to control how the quota is looked up:

box = : Use GETQUOTAROOT 
root = : Use GETQUOTA 


Example:

plugin {
  quota = imapc:root=User Quota
}