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.

Settings

`imapc_cmd_timeout`

Default	`5 mins`
Value	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`
Value	unsigned integer

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

`imapc_connection_retry_interval`

Default	`1 secs`
Value	time (milliseconds)

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

`imapc_features`

Default	[None]
Value	string
Changes	Changed: 2.4.0 Several features are now automatically enabled and the respective flags dropped. In their place new flags to disable these features were added.

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

Features

no-acl

If the imap-acl plugin is loaded, the imapc acl feature is automatically enabled. With it IMAP ACL commands (MYRIGHTS, GETACL, SETACL, DELETEACL) are proxied to the imapc remote location. Note that currently these commands are attempted to be used even if the remote IMAP server doesn't advertise the ACL capability.

To disable this feature either unload the imap-acl plugin or provide this feature.

Changed: 2.4.0

Earlier versions had an "acl" feature, which is now enabled by default.

no-delay-login: Immediately connect to the remote server. By default this is delayed until a command requires a connection.

Changed: 2.4.0

Earlier versions had a "delay-login" feature, which is now enabled by default.

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.

no-modseq: Disable access to MODSEQ and HIGHESTMODSEQ fields. By default these fields are available if the remote server advertises the CONDSTORE or the QRESYNC capability. If modseqs are disabled, or not supported by the new server, they can still be used if imapc is configured to have local index files.

Changed: 2.4.0

Earlier versions had a "modseq" feature, which is now enabled by default.

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:<INIT>:<MAX>:<SHRINK>

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 shrunk 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

no-fetch-bodystructure: Disable fetching of IMAP BODY and BODYSTRUCTURE from the remote server. Instead, the whole message body is fetched to regenerate them.

Changed: 2.4.0

Earlier versions had a "fetch-bodystructure" feature, which is now enabled by default.

no-fetch-headers: Disable fetching of specific message headers from the remote server using the IMAP FETCH BODY.PEEK[HEADER.FIELDS(...)] command. Instead, the whole header is fetched and the wanted headers are parsed from it.

Changed: 2.4.0

Earlier versions had a "fetch-headers" feature, which is now enabled by default.

no-fetch-size: Disable fetching of message sizes from the remote server using the IMAP FETCH RFC822.SIZE command. Instead, the whole message body is fetched to calculate the size.

Changed: 2.4.0

Earlier versions had a "rfc822.size" feature, which is now enabled by default.

no-metadata: Disable the detection of the METADATA capability from the remote server. The client will receive a NO [UNAVAILABLE] response for any request that requires access to metadata on the remote server (the same happens if the server does not announce the capability at all).

no-search: Disable searching messages using the IMAP SEARCH command. Instead, all the message headers/bodies are fetched to perform the search locally.

Changed: 2.4.0

Earlier versions had a "search" feature, which is now enabled by default.

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.

DANGER

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.

no-qresync Added: 2.4.0: This can be used to work around a Zimbra bug where it doesn't send untagged "OK [CLOSED]" imap-resp-code when selecting a folder.

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 this should no longer be a problem and there's probably no need to enable this workaround.

`imapc_host`

Default	[None]
Value	string

The remote IMAP host to connect to.

`imapc_list_prefix`

Default	[None]
Value	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	[None]
Value	string
See Also	`imapc_password` `imapc_user`

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.

`imapc_max_idle_time`

Default	`29 mins`
Value	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	[None]
Value	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	[None]
Value	string
See Also	`imapc_master_user` `imapc_user`

The authentication password for the remote IMAP server.

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

`imapc_port`

Default	`143`
Value	unsigned integer

The port on the remote IMAP host to connect to.

`imapc_rawlog_dir`

Default	[None]
Value	string
See Also	rawlog

Log all IMAP traffic input/output to this directory.

`imapc_sasl_mechanisms`

Default	`plain`
Value	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.

imapc_sasl_mechanisms = external plain login

`imapc_ssl`

Default	`no`
Value	string
Allowed Values	`noimapsstarttls`

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`
Value	boolean
See Also	`imapc_ssl`

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.

`imapc_user`

Default	[None]
Value	string
See Also	`imapc_master_user` `imapc_password`

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

Mail user variables can be used.

Configuration Example

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

# In-memory index files:
mail_location = imapc:

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

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. 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 = <mailbox>: Use GETQUOTAROOT <mailbox>
root = <name>: Use GETQUOTA <name>

Example:

plugin {
  quota = imapc:root=User Quota
}

Authentication

Databases

Mechanisms

Mail Delivery

Events

Guides

Mailbox

Formats

Sieve

Extensions

SQL

Users

Guides

Lua Support

Index Files

Imapc Mailbox Format

Settings

`imapc_cmd_timeout`

`imapc_connection_retry_count`

`imapc_connection_retry_interval`

`imapc_features`

`imapc_host`

`imapc_list_prefix`

`imapc_master_user`

`imapc_max_idle_time`

`imapc_max_line_length`

`imapc_password`

`imapc_port`

`imapc_rawlog_dir`

`imapc_sasl_mechanisms`

`imapc_ssl`

`imapc_ssl_verify`

`imapc_user`

Configuration Example

Quota

Databases

Mechanisms

Formats

Extensions

Imapc Mailbox Format ​

Settings ​

imapc_cmd_timeout

imapc_connection_retry_count

imapc_connection_retry_interval

imapc_features

imapc_host

imapc_list_prefix

imapc_master_user

imapc_max_idle_time

imapc_max_line_length

imapc_password

imapc_port

imapc_rawlog_dir

imapc_sasl_mechanisms

imapc_ssl

imapc_ssl_verify

imapc_user

Configuration Example ​

Quota ​

Imapc Mailbox Format

Settings

`imapc_cmd_timeout`

`imapc_connection_retry_count`

`imapc_connection_retry_interval`

`imapc_features`

`imapc_host`

`imapc_list_prefix`

`imapc_master_user`

`imapc_max_idle_time`

`imapc_max_line_length`

`imapc_password`

`imapc_port`

`imapc_rawlog_dir`

`imapc_sasl_mechanisms`

`imapc_ssl`

`imapc_ssl_verify`

`imapc_user`

Configuration Example

Quota