Crate rusmes_core 

rusmes-core — Mailet Processing Engine for RusMES

rusmes-core is the central mail-processing library for RusMES, providing a composable pipeline of matchers and mailets that evaluate and transform incoming mail messages. It is modelled after the Apache James mailet API but implemented from scratch in async Rust.

Architecture

Mail processing flows through a Processor that applies a sequence of ProcessingSteps. Each step pairs a Matcher (decides whether to act) with a Mailet (decides what to do).

 ┌─────────┐     ┌───────────────────────────────────────────────────┐
 │  Mail   │────▶│  Processor                                        │
 └─────────┘     │   Step 1: Matcher → Mailet (e.g. SpfCheck)        │
                 │   Step 2: Matcher → Mailet (e.g. DkimVerify)      │
                 │   Step 3: Matcher → Mailet (e.g. SieveMailet)     │
                 │   Step N: …                                       │
                 └───────────────────────────────────────────────────┘

Included Mailets

Mailet	Purpose
mailets::AddHeaderMailet	Append arbitrary headers
mailets::BounceMailet	RFC 3464 DSN bounce generation
mailets::DkimVerifyMailet	DKIM signature verification (RFC 6376)
mailets::DmarcVerifyMailet	DMARC policy enforcement (RFC 7489)
mailets::DnsblMailet	DNS-based block-list lookups
mailets::ForwardMailet	Forwarding with loop detection
mailets::GreylistMailet	Greylisting anti-spam
mailets::LegalisMailet	Legal archiving with RFC 3161 timestamps
mailets::LocalDeliveryMailet	Local mailbox delivery
mailets::OxifyMailet	AI-powered mail enrichment
mailets::RemoteDeliveryMailet	SMTP relay delivery (Pure Rust / rustls)
mailets::RemoveMimeHeaderMailet	Strip MIME headers by pattern
mailets::SieveMailet	RFC 5228 Sieve script filtering
mailets::SpamAssassinMailet	SpamAssassin integration
mailets::SpfCheckMailet	SPF policy checking (RFC 7208)
mailets::VirusScanMailet	ClamAV / virus-scan integration

Included Matchers

Matcher	Purpose
CompositeAll / CompositeAny	Boolean composition of other matchers
HasAttachment	True when mail has MIME attachments
HeaderContains	True when a header contains a substring
IsInBlacklist	Sender/recipient on a configurable deny-list
IsInWhitelist	Sender/recipient on a configurable allow-list
RecipientIsLocal	True when recipient is a local domain
RemoteAddress	True when client IP matches a CIDR range
SenderIs	Exact or wildcard sender address match
SizeGreaterThan	True when message exceeds a byte threshold

Protocol Support

• SMTP – mail reception and relay (rusmes-smtp)
• IMAP4 – mail access (rusmes-imap)
• JMAP – JSON Meta Application Protocol (rusmes-jmap)
• POP3 – legacy mail retrieval (rusmes-pop3)

Feature Flags

This crate currently has no optional feature flags; all components are always compiled.

Quick-start Example

use rusmes_core::{Processor, ProcessingStep};
use rusmes_proto::MailState;
use std::sync::Arc;

// Build a basic processor that evaluates mail in the Root state
let mut processor = Processor::new("transport", MailState::Root);

// Steps are (matcher, mailet) pairs; add them via add_step(ProcessingStep::new(…))
// See individual mailet and matcher types in the rusmes_core::mailets /
// rusmes_core::matchers modules for concrete implementations.

Re-exports

pub use bounce::generate_bounce;

pub use queue::FilesystemQueueStore;

pub use queue::MailQueue;

pub use queue::Priority;

pub use queue::PriorityConfig;

pub use queue::PriorityQueue;

pub use queue::PriorityStats;

pub use queue::QueueEntry;

pub use queue::QueueEntryData;

pub use queue::QueueStats;

pub use queue::QueueStore;

pub use rate_limit::RateLimitConfig;

pub use rate_limit::RateLimiter;

pub use sieve::SieveAction;

pub use sieve::SieveCommand;

pub use sieve::SieveContext;

pub use sieve::SieveInterpreter;

pub use sieve::SieveScript;

pub use sieve::SieveTest;

Modules

bounce

Bounce message generation

dsn

DSN (Delivery Status Notification) utilities - RFC 3464 and RFC 3463

factory

Factory for creating mailets and matchers from configuration

mailets

Standard mailet implementations

matchers

Standard matcher implementations

queue

Mail queue management with retry logic and priority support

rate_limit

Rate limiting for connection and message processing

sieve

Sieve mail filtering language support (RFC 5228)

Structs

MailProcessorRouter

Routes mail between processors based on state

MailetConfig

Mailet configuration

ProcessingStep

Matcher-Mailet pair

Processor

Named processor chain for a specific state

Enums

MailetAction

Actions a mailet can take after processing a mail

Traits

Mailet

Core mailet trait - message processing unit

Matcher

Matcher trait - filter recipients based on criteria