Horde ActiveSync

PHP library implementing the Microsoft Exchange ActiveSync (EAS) protocol, versions 2.5 through 16.1. It decodes WBXML requests from mobile clients, drives synchronization through a pluggable backend driver, and encodes WBXML responses — including streamed Sync response delivery for clients with hard read timeouts.

In a typical Horde deployment, this package is the protocol engine. The data backend lives in horde/core as Horde_Core_ActiveSync_Driver, which talks to IMAP (mail), Kronolith (calendar), Turba (contacts), Nag (tasks), and Mnemo (notes). The library itself has no Horde application dependencies at runtime and can be embedded with a custom driver.

Documentation

The documentation is split by audience:

You are…	You want to…	Read
Administrator / end user	Enable ActiveSync, configure protocol versions, streaming, logging, the web server endpoint, and per-user policy	doc/configuration.md
Library user / integrator	Embed the library in your own product: server object, driver API, state backends, custom backends	doc/integration.md
ActiveSync developer	Understand the internals: components, request lifecycle, Sync anatomy, state machine, tests	doc/architecture.md

Cross-cutting references, useful to all three:

Topic	Read
Supported EAS protocol versions, negotiation, and what each version adds	doc/protocol-versions.md
Streamed Sync response delivery — design, error model, tuning	doc/sync-streaming.md
Heartbeat polling and export performance — batched STATUS, read-only state loads, bulk export	doc/sync-performance.md
Open work and the Horde 6 roadmap	doc/todo.md

At a glance

Mobile client (Outlook, iOS Mail, Gmail, …)
        │  HTTPS POST, WBXML body
        ▼
Web server  →  /Microsoft-Server-ActiveSync  (rewritten to Horde rpc.php)
        │
        ▼
Horde_Rpc_ActiveSync                (horde/rpc)
        │
        ▼
Horde_ActiveSync                    ← this library
  ├── Request handlers (Sync, FolderSync, Ping, …)
  ├── Message classes (Appointment, Mail, Contact, …)
  ├── WBXML encoder/decoder
  └── Horde_ActiveSync_Driver_Base  (abstract backend API)
        │
        ▼
Horde_Core_ActiveSync_Driver        (horde/core, in a Horde deployment)
  └── Horde_Core_ActiveSync_Connector → Horde apps / IMAP

Protocol versions

All EAS versions from 2.5 to 16.1 are implemented and production-supported. Clients negotiate down to the server's advertised ceiling; the ceiling is configurable globally, per user, and per device. Details, the version negotiation mechanics, and a per-version feature delta are in doc/protocol-versions.md.

Version	Notes
2.5	Baseline; reduced command set (no Settings, ItemOperations, Find)
12.0 / 12.1	AirSyncBase bodies, provisioning 2, empty/hanging Sync, SyncCache
14.0 / 14.1	Conversations, reply/forward state, rights management, body parts
16.0	Calendar instance model, drafts sync, Find, AirSyncBase:Location
16.1	Meeting time proposals, account-only remote wipe

Feature highlights

• Mail: folder & message sync, flags, drafts (incl. EAS 16 draft editing/sending), send/reply/forward, attachments, meeting requests, mailbox Find with KQL parsing, GAL search
• Calendar: full recurrence + exceptions, attendees, meeting responses, EAS 16 instance model, meeting time proposals (16.1)
• Contacts / Tasks / Notes: full CRUD sync incl. task recurrence
• Device management: provisioning & policies, remote wipe (full and account-only), per-device protocol ceilings, per-device logging
• State: SQL (default) or MongoDB backends, sync-key/modseq change tracking, Ping long-poll, SyncCache
• Delivery: optional streamed Sync responses (chunked HTTP) with deferred up-sync import and WBXML keep-alives, so clients with ~30 s read timeouts survive large batches — see doc/sync-streaming.md
• Efficiency: heartbeat polling batches all mailbox status checks into one IMAP round trip and reuses memoized, lock-free state reads; message export prefetches email items in batches — see doc/sync-performance.md

Package layout

lib/Horde/ActiveSync.php          Server class and protocol constants
lib/Horde/ActiveSync/
  Request/                        EAS command handlers
  Message/                        Item type WBXML mappings
  State/                          Sync state persistence (SQL, Mongo)
  Wbxml/                          Encoder, decoder, code pages
  Imap/                           IMAP-to-EAS message building
  Find/                           EAS 16.0 Find command helpers
  Driver/                         Base, Mock backends
migration/                        SQL schema for state tables
doc/                              Documentation (see index above)
test/unit/                        PHPUnit tests

License

GPL-2.0-only. See LICENSE.

References

• Microsoft Exchange ActiveSync protocol docs
• Horde ActiveSync wiki