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

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

imapc_connection_retry_interval

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

imapc_features

  • Default: <empty>

  • Values: String

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

Changed in version 2.4.0 (CE): Several features are now automatically enabled and the respective flags dropped. In their place new flags to disable these features were added.

Changed in version 3.0.0 (Pro): Several features are now automatically enabled and the respective flags dropped. In their place new flags to disable these features were added.

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 in version 2.4.0 (CE): Earlier versions had an “acl” feature, which is now enabled by default.

Changed in version 3.0.0 (Pro): 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 in version 2.4.0 (CE): Earlier versions had a “delay-login” feature, which is now enabled by default.

Changed in version 3.0.0 (Pro): 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 in version 2.4.0 (CE): Earlier versions had a “modseq” feature, which is now enabled by default.

Changed in version 3.0.0 (Pro): 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 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

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 in version 2.4.0 (CE): Earlier versions had a “fetch-bodystructure” feature, which is now enabled by default.

Changed in version 3.0.0 (Pro): 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 in version 2.4.0 (CE): Earlier versions had a “fetch-headers” feature, which is now enabled by default.

Changed in version 3.0.0 (Pro): 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 in version 2.4.0 (CE): Earlier versions had a “rfc822.size” feature, which is now enabled by default.

Changed in version 3.0.0 (Pro): 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 in version 2.4.0 (CE): Earlier versions had a “search” feature, which is now enabled by default.

Changed in version 3.0.0 (Pro): 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.

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.

imapc_host

  • Default: <empty>

  • Values: String

The remote IMAP host to connect to.

imapc_list_prefix

  • Default: <empty>

  • 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: <empty>

  • 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: <empty>

  • 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

The port on the remote IMAP host to connect to.

imapc_rawlog_dir

  • Default: <empty>

  • 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

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: <empty>

  • 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 = <mailbox>: Use GETQUOTAROOT <mailbox>

  • root = <name>: Use GETQUOTA <name>

Example:

plugin {
  quota = imapc:root=User Quota
}