IMAP configuration

Yarilo implements IMAP4rev2 (RFC 9051) with backward compatibility to IMAP4rev1 (RFC 3501).

Listeners: services.imaps (implicit TLS, port 993) and services.imap (STARTTLS, port 143). See Services configuration for listener-level settings (port, ssl_mode, haproxy_protocol, etc.).

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protocol.imap

Protocol-level behaviour, shared across both IMAP listeners.

imap_idle_notify_interval

Default

120

Type

integer, seconds

Helm

protocol.imap.imap_idle_notify_interval

Interval between unsolicited EXISTS/RECENT responses during IDLE (RFC 2177 keepalive). 0 disables them.

imap_max_line_length

Default

65536

Type

integer, bytes

Helm

protocol.imap.imap_max_line_length

Maximum IMAP command line length. 0 is unlimited.

imap_id_send

Default

name *

Type

string

Helm

protocol.imap.imap_id_send

Space-separated key-value pairs sent in the ID response (RFC 2971). * means the server's own value. An empty string turns the ID extension off after login.

login_greeting

Default

none

Type

string

Helm

protocol.imap.login_greeting

Replaces IMAP server ready in the backend's greeting. Clients behind a login proxy see yarilo-imap-login's own greeting, Yarilo Login ready, which this key does not change. Empty keeps the default.

imap_logout_format

Default

none

Type

string

Helm

protocol.imap.imap_logout_format

Format of the line logged at session end; the variables are listed below. Empty logs no stats line.

imap_quota

Default

true

Type

boolean

Helm

protocol.imap.imap_quota

Advertise and serve the QUOTA extension (RFC 9208). Independent of quota enforcement.

imap_special_use_defaults

Default

Archive: \Archive, Drafts: \Drafts, Junk: \Junk, Sent: \Sent, Trash: \Trash

Type

map

Helm

protocol.imap.imap_special_use_defaults

Folder name (case-sensitive) to its RFC 6154 attribute, e.g. Sent: "\\Sent". A user's own CREATE (USE …) wins.

imap_client_workarounds

Default

[]

Type

list

Values

tb-extra-mailbox-sep tb-lsub-flags

Also accepted as

client_workarounds

Helm

protocol.imap.client_workarounds

Compatibility shims for clients that break the protocol.

imap_logout_format variables

Variable	Description
%{deleted}	Number of messages marked \Deleted in the session.
%{expunged}	Number of messages expunged (removed from disk).
%{fetch_hdr_count}	Number of header fetch operations.
%{fetch_hdr_bytes}	Bytes transferred for header fetches.
%{fetch_body_count}	Number of body fetch operations.
%{fetch_body_bytes}	Bytes transferred for body fetches.

Example:

protocol:
  imap:
    imap_logout_format: "in=%{fetch_hdr_bytes}+%{fetch_body_bytes} expunged=%{expunged}"

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Supported IMAP extensions

Feature coverage is the exhaustive list of what the server advertises. This table explains the ones that need it.

IMAP4rev2 also brings ENABLE, SASL-IR, LITERAL+, SEARCHRES and STATUS=SIZE; LIST-EXTENDED, LIST-STATUS, CREATE-SPECIAL-USE and SORT (RFC 5256, without SORT=DISPLAY) are advertised too.

Extension	RFC	Notes
IDLE	RFC 2177	Server-push new-mail notifications.
MOVE	RFC 6851	Atomic move (no COPY + STORE + EXPUNGE round-trip).
CONDSTORE	RFC 7162	MODSEQ flag, conditional STORE.
QRESYNC	RFC 7162	Fast mailbox resync after reconnect.
UIDPLUS	RFC 4315	APPENDUID / COPYUID response codes.
UNSELECT	RFC 3691	Close mailbox without expunge.
NAMESPACE	RFC 2342	Shared / Other Users namespaces.
QUOTA	RFC 9208	Per-user storage quota. Advertised while imap_quota is on (the default).
ACL	RFC 4314	Per-mailbox access control lists. Advertised only with acl.enabled. A body FETCH sets \Seen only for a reader holding s; with r alone the body is served and the flag left as it is.
BINARY	RFC 3516	Binary content transfer.
THREAD	RFC 5256	Threading of the searched messages, both algorithms: THREAD=REFERENCES (ancestry from References / In-Reply-To, then joining by base subject) and THREAD=ORDEREDSUBJECT (base subject alone). Computed per command from message headers.
ESEARCH	RFC 4731	Extended SEARCH with MIN/MAX/COUNT.
NOTIFY	RFC 5465	Event-based notifications. NOTIFY SET/NONE parsed with all mailbox filters; the selected mailbox honours SELECTED / SELECTED-DELAYED (MessageNew / MessageExpunge / FlagChange), suppressing the unsolicited responses the client did not request (RFC 5465 §5). Non-selected mailbox filters (PERSONAL / INBOXES / SUBSCRIBED / SUBTREE / MAILBOXES) are watched via the pkg/locks event bus and their MessageNew / MessageExpunge / FlagChange activity is reported as untagged * STATUS (RFC 5465 §6), delivered during IDLE and before the next command's tagged response. The watched set is re-evaluated dynamically: mailboxes created, renamed or subscribed after NOTIFY SET join or leave the set live (via the per-user mlist: event key). Mailbox-level events — MailboxName (create / delete / rename, the last with OLDNAME) and SubscriptionChange (subscribe / unsubscribe) — are reported as untagged * LIST responses (RFC 5465 §5) when requested. AnnotationChange / metadata events are not yet reported.
SPECIAL-USE	RFC 6154	\Sent, \Drafts, \Trash folder flags.
ID	RFC 2971	Server identity advertisement. Always offered before login; after login only while imap_id_send is non-empty.
OBJECTID	RFC 8474	Stable object identifiers: MAILBOXID (SELECT/EXAMINE response code + STATUS item, from the folder GUID), EMAILID (FETCH, from the message GUID), THREADID (FETCH, the conversation a message belongs to; NIL for accounts whose threading data has not been built yet). IDs are 32 lowercase hex chars of the 128-bit GUID; they survive RENAME.
METADATA	RFC 5464	Advertised only when a metadata dict is configured. Server and per-mailbox annotations (GETMETADATA / SETMETADATA). State lives in cfg.Dicts["metadata"] (pkg/dict). Keys: priv/box/<folder_guid>/<entry> and shared/box/<folder_guid>/<entry>; server-scope entries live under INBOX's GUID with a vendor/yarilo/pvt/server/ prefix so they cannot collide with INBOX mailbox attributes.