I made another test call, which should go to voice mail. The logs imply that the call did get routed to voice mail, but I could not hear any audio and the VoIP connection never hangs up.
Here is the log:
07:37:14.871 FaxCfg::updateContact [CM504008]: Fax Service: registered as sip:888@3CXPhoneSystem with contact sip:
[email protected]:5100;user=phone
07:37:14.100 FaxCfg::updateContact [CM504010]: Fax Service: unregistered contact sip:888:5100;user=phone
07:33:47.874 LineCfg::getInboundTarget [CM503011]: Inbound out-of-office hours' rule for LN:10001 forwards to VM:100
07:33:47.824 CallCtrl:

nLegConnected [CM503007]: Call(1): Device joined: sip:
[email protected]:5060
07:33:47.814 MediaServerReporting::SetRemoteParty [MS210003] C:1.1:Answer provided. Connection(transcoding mode):82.29.210.191:9000(9001)
07:33:47.423 CallCtrl:

nLegConnected [CM503007]: Call(1): Device joined: sip:
07:33:47.233 MediaServerReporting::SetRemoteParty [MS210000] C:1.1:Offer received. RTP connection: 213.166.5.134:22260(22261)
07:33:47.213 CallCtrl:

nSelectRouteReq [CM503004]: Call(1): Calling: IVR:RecordMessage@[Dev]
07:33:47.213 CallCtrl:

nSelectRouteReq [CM503010]: Making route(s) to [sip:
[email protected]:5060;user=vmail]
07:33:47.183 CallLeg::setRemoteSdp Remote SDP is set for legC:1.1
07:33:47.183 Line:

rintEndpointInfo [CM505003]: Provider:[MidasTelecom] Device info: Device Not Identified: User Agent not matched; Capabilities:[reinvite, replaces, able-no-sdp, recvonly] UserAgent: [MSSGW] Transport: [sip:82.29.210.191:5060]
07:33:47.183 LineCfg::getInboundTarget [CM503011]: Inbound out-of-office hours' rule for LN:10001 forwards to VM:100
07:33:46.051 CallCtrl:

nIncomingCall [CM503001]: Call(1): Incoming call from 01158759709@(Ln.10001@MidasTelecom) to [sip:
[email protected]:5060;user=vmail]
07:33:45.440 LineCfg::getInboundTarget [CM503011]: Inbound out-of-office hours' rule for LN:10001 forwards to VM:100
07:33:45.120 CallLeg:

nNewCall [CM500002]: Info on incoming INVITE:
INVITE sip:
[email protected] SIP/2.0
Via: SIP/2.0/UDP 213.166.5.130;branch=z9hG4bKb836.2d1bbd06.0
Via: SIP/2.0/UDP 213.166.5.134:5060;branch=z9hG4bK1ADBF0821BB
Max-Forwards: 14
Record-Route: [sip:213.166.5.130;lr=on;ftag=609CBC6C-263C]
Contact: [sip:
[email protected]:5060]
To: [sip:
[email protected]]
From: "01158759709"[sip:
[email protected]];tag=609CBC6C-263C
Call-ID:
[email protected]
CSeq: 101 INVITE
Expires: 180
Min-SE: 1800
Allow: INVITE, BYE, CANCEL, ACK
Date: Wed, 02 Apr 2008 06:33:42 gmt
Supported: 100rel, timer, resource-priority, replaces
Timestamp: 1207118022
User-Agent: MSSGW
Allow-Events: telephone-event
Content-Length: 0
Remote-Party-ID: [sip:
[email protected]];party=calling;screen=yes;privacy=off