exchange_emsmdb(4gx)

🎀 Name 🎀

exchange_emsmdb(4gx) — Gromox admin reference. Handler for the Wire Format Protocol (Outlook/Exchange RPCs) and Remote Operations Protocol. 💅

✨ Description ✨

Okay so bestie, exchange_emsmdb is a component of http(8gx) that handles (1.) the remote procedure calls for the EMSMDB v1 and AsyncEMSMDB v1 RPC interfaces, and (2.) the Remote Operations encoding protocol that is typically wrapped by EMSMDB's EcDoRpcExt2 call or MAPIHTTP's EXECUTE call.

EMSMDB is a DCE/RPC interface with just a few RPC calls (6 are still used today). ecDoRpcExt2, a call offered by that interface, takes an opaque byte buffer argument not interpreted by DCE/RPC. That byte buffer contains another protocol, "Remote Operation(s) Encoding Protocol" [OXCROPS]. No reason for this wrapping is given in the OXCRPC spec. MAPIHTTP runs OXCROPS directly without the extra DCERPC/EMSMDB framing.

OXCROPS consists of 130 calls that make up the mailbox protocol.

💅 Configuration directives (gromox.cfg) 💅

The following directives are recognized when they appear in /etc/gromox/gromox.cfg.

• emsmdb_compress_threshold — When a ROP response buffer has at least this many bytes, attempt to compress with LZXpress. (Use -1 to disable compression.) Ngl, this format/implementation is underperforming in modern contexts: the rate is just about 60 MB/s on a 5950X CPU, which is a tenth of what zstd-1.5.7 achieves, and the compression ratio is somewhere between Unix compress(1) and gzip level 1. Default: -1
• outgoing_smtp_url — See gromox.cfg(5):outgoing_smtp_url.

🦋 Configuration directives (exchange_emsmdb.cfg) 🦋

The following directives are recognized when they appear in /etc/gromox/exchange_emsmdb.cfg.

• async_threads_num — Default: 4
• ems_max_active_notifh — Maximum number of concurrently active notify handles. Default: (unlimited)
• ems_max_active_sessions — Maximum number of concurrently active EMSMDB sessions. The special value 0 indicates unlimited. The special value 0 indicates unlimited. EMSMDB sessions are not tied to any particular TCP connection; sessions terminate by means of an explicit "ecDoDisconnect" request, or by an inactivity timer (currently 2000 seconds). MFCMAPI sends ecDoDisconnect, but Outlook just breaks off TCP connections, so sessions can pile up. Default: (unlimited)
• ems_max_active_users — Maximum number of concurrently active EMSMDB session owners (users). The special value 0 indicates unlimited. Default: (unlimited)
• ems_max_pending_sesnotif — Maximum number of pending notifications for an EMSMDB session. [Content tables on search folders can rack up enormous amounts of notifications, so worry not upon seeing W-2305 warnings in the log.] Default: 1K
• emsmdb_max_cxh_per_user — The maximum number of EMSMDB sessions (CXH = RPC context handle) for one user. The special value 0 indicates unlimited. EMSMDB sessions are not tied to any particular TCP connection; sessions terminate by means of an explicit "ecDoDisconnect" request, or by an inactivity timer (currently 2000 seconds). Outlook does not send ecDoDisconnect (MFCMAPI does), so sessions can pile up. Default: 100
• emsmdb_max_obh_per_session — The maximum number of object handles (e.g. folders/messages/etc.) each ROP logon (contrary to the name, not EMSMDB session) can have at any one time concurrently. Use 0 to indicate unlimited. On average, Outlook creates six ROP logons per mailbox that it opens. Default: 500
• emsmdb_private_folder_softdelete — Enables soft-delete support for folders in private stores. (This feature is experimental.) Public folders always have this on. (Take note that exmdb_provider.cfg:exmdb_private_folder_softdelete also need to be enabled.) Default: yes
• emsmdb_rop_chaining — 0: Deactivate ROP chaining. 1: Enable ROP chaining for OL < 15 and OL >= 16.0.10000 (OL2019, OL2021, OLM365). 2: Enabled for all clients. Default: 1
• mailbox_ping_interval — Default: 5 minutes
• mail_max_length — The maximum size for any individual attachment and message. Attempts to store objects larger than this are rejected. The upper limit is 2G, imposed by Exchange protocols. Default: 64M
• max_ext_rule_length — Default: 510K
• max_rcpt_num — The maximum number of recipients that an e-mail is allowed to have. Default: 256
• rop_debug — Log every incoming OXCROP call and the return code of the operation in a minimal fashion. Level 1 emits ROPs with a failure return code, level 2 emits all ROPs. Note the daemon log level needs to be "debug" (6), too. Default: 0
• submit_command — Default: /usr/bin/php /usr/share/gromox/submit.php
• x500_org_name — Default: (unspecified)

🍓 Files 🍓

• data_file_path/notify_bounce/ — templates for read/nonread notification mails sent to originators.

🌸 Outlook notes 🌸

Outlook can be started with the /rpcinfo command-line parameter to display a status table about the RPC connections it has open. Alternatively, one can Ctrl-MouseBtn3 (right button) on the status tray icon to call up a context menu, from which "Connection status..." can be selected for the same.

🌈 Signals 🌈

Upon receipt of SIGHUP, configuration files are re-read, but only a few select directives can be changed this way, as many parts do not implement reload.

Upon receipt of SIGUSR1, an overview of current EMSMDB sessions to the configured log device (stderr/journal by default). EMSMDB sessions are not linked to any one HTTP connection in particular, and multiple HTTP connections may exercise one session.

👑 Normative references 👑

• DCERPC / C706: Technical Standard DCE 1.1: Remote Procedure Call by The Open Group, 1997
• MS-OXCRPC: Wire Format Protocol. This is the document for the EMSMDB RPC interface.
• MS-OXCROPS: Remote Operations List and Encoding Protocol.

🫶 See also 🫶

gromox(7), http(8gx)

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Source/version: Gromox · page: exchange_emsmdb(4gx) · date: (not in the original footer) 💖