exchange_emsmdb(4gx) — http(8gx) processing plugin for the Wire Format Protocol (Outlook/Exchange RPCs).


exchange_emsmdb is a processing plugin for http(8gx) which handles the remote procedure calls for the EMSMDB v1 and AsyncEMSMDB v1 RPC interfaces, as well as OXCROPS as issued by the EcDoRpcExt2 call or the MAPIHTTP 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 EMSMDB framing.

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

Configuration directives

The usual config file location is /etc/gromox/exchange_emsmdb.cfg.


Default: 4


Default: 1000


Default: 4K

Maximum number of concurrently active notify handles.
Default: (unlimited)
Maximum number of concurrently active EMSMDB session handles.
Default: (unlimited)
Maximum number of concurrently active mailbox identities.
Default: (unlimited)
Maximum number of pending notifications for an EMSMDB session. (If a client accrues too many pending notifications, there may be something wrong with the client.)
Default: 1K
The maximum number of RPC context handles any one user can have at any one time.
Default: 100
The maximum number of object handles each session can have at any one time (e.g. folders/messages/etc. open simultaneously). There is one session for each mailbox opened.
Default: 500
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: no
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

Default: 5 minutes

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

Default: 510K

The maximum number of mails that a mailbox is allowed to have.
Default: 1000000
The maximum number of recipients that an e-mail is allowed to have.
Default: 256
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

Default: ;

SMTP server hostname or address to contact for outgoing mail.
Default: ::1
SMTP server TCP port number to connect to for outgoing mail.
Default: 25

Default: /usr/bin/php /usr/share/gromox/sa/submit.php


Default: (unspecified)


  • data_file_path/notify_bounce/: response templates for when mail cannot be delivered

  • data_file_path/msgchg_grouping/.txt*

Outlook notes

Outlook can be started with the /rpcinfocommand-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.


When SIGUSR1 is received by this module, it will dump 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