bongo/docs/sieve.md

Sieve filtering and ManageSieve

Bongo stores each user's server-side mail rules independently from the mail payloads. bongosieve provides the ManageSieve management protocol, while bongorules evaluates the active script as mail passes through the Queue. Thunderbird and other ManageSieve clients can therefore maintain filters without editing server files.

Listener and authentication

ManageSieve is disabled by the base template until it is required. Its suffixless sieve document has conservative loopback defaults:

{
  "enabled": false,
  "listen_address": "127.0.0.1",
  "port": 4190,
  "allow_legacy_tls": false,
  "proxy_protocol_enabled": false,
  "proxy_protocol_networks": [],
  "maximum_script_size": 1048576,
  "maximum_connections": 64
}

The greeting offers STARTTLS; GNU GSASL mechanisms are advertised only after TLS. Authentication uses the same Bongo user and app-password policy as the mail protocols, with the Sieve service scope. Cleartext received after a STARTTLS command is discarded before negotiation. PROXY protocol has the same source-restricted rules as the other mail listeners.

Management protocol

The RFC 5804 service implements CAPABILITY, STARTTLS, AUTHENTICATE, HAVESPACE, PUTSCRIPT, CHECKSCRIPT, LISTSCRIPTS, GETSCRIPT, SETACTIVE, RENAMESCRIPT, DELETESCRIPT, NOOP, and LOGOUT. Script names and literals are bounded, syntax is validated before activation, an active script cannot be deleted accidentally, and scripts are isolated by authenticated user.

The implementation advertises fileinto, envelope, body, variables, vacation, and vacation-seconds. envelope and body (RFC 5173) are not implemented by the stock Mailutils Sieve engine at all -- confirmed directly against Mailutils' own sieve reference tool, independent of Bongo -- so the Gentoo net-mail/mailutils ebuild this project builds against carries local patches adding both: a small require.c fix so require ["envelope"]; resolves the standard test Mailutils already implements but never lets a bare require reach, and a new body.c test module (using only Mailutils' own MIME/message API, no new dependency) implementing :raw, :content <types>, and :text (default) per RFC 5173. Upstream Mailutils' envelope test only ever resolved the "from" envelope-part (retrieve_envelope() hard-coded that one string and returned no-match for anything else, "to" included); a second local patch adds a mu_envelope_set_recipient()/mu_envelope_sget_recipient() accessor pair to libmailutils mirroring the existing sender accessor 1:1 (same struct/callback shape, same lazy header-derived fallback via a new message_envelope_recipient(), checking X-Envelope-Recipient, X-Envelope-To, Delivered-To, X-Original-To, and To in that order), so "to" now resolves the same way "from" always did. Neither envelope part is a true SMTP-level value -- Bongo hands Mailutils raw message bytes with no separate envelope channel -- so both are header-derived best-effort proxies, consistent with each other. All of this is verified against Mailutils' own upstream Sieve test suite (zero regressions) plus live execution; see the release testing evidence for SIEVE-04. Actions include keep, discard, file into a folder, redirect, reject, and vacation response. Vacation history is durable so repeated delivery does not generate an immediate reply loop. Scripts and vacation state live in the owning user's authoritative Bongo Store and are accessed by bongosieve and bongorules through NMAP. Include the user's complete Store directory in backups.

Filters in Webmail

The Web filter editor and ManageSieve are two interfaces to the same intended user rule model. A filter may match senders or other message properties and deliver matching messages to a folder such as Family. Mailing-list recognition is one possible filter condition, not a separate replacement for the filter system. Future JMAP support must map to the same rules rather than creating a third incompatible store.

Test script upload, syntax rejection, activation, rename, retrieval, deletion, folder delivery, redirect, reject, vacation deduplication, and quota limits before exposing the service. The 0.7 release cases are SIEVE-01 through SIEVE-05 in release-testing-0.7.md.