How Voicemail Works; Checking Voicemail From An External Number - Linksys SPA9000 Administration Manual

Three parameters must be configured on the SPA9000 for each line to support these
operations: <Mailbox Deposit URL>, <Mailbox Manager URL>, and <Mailbox Subscribe URL>.
The mailbox ID should be set to the extension number.
Note
Voicemail service may be offered by a service provider different from the ITSP. For example, you
can configure Line 1, 2, and 3 with accounts on an ITSP, but configure Line 4 an account with a
different Internet voicemail service provider (IVMSP). The SPA9000 can be configured to bridge
calls between the ITSP and the IVMSP when necessary (when depositing or checking voicemail
by an external caller) using the <VMSP Bridge> parameter on each line interface.

How Voicemail Works

When a user checks voicemail from a client station, the SPA9000 sends an INVITE on its behalf to
the configured <Mailbox Manage URL>. For example:
INVITE sip:mailbox-manage-url SIP/2.0
Via: SIP/2.0/UDP 192.168.2.205:5060;branch=z9hG4bK-171eb6b5
From: <sip:37683102@sip.myitsp.com>;tag=300704dd2590d20bo2;ref=5031;mbid=53371
To: <sip:mailbox-manage-url>
Call-ID: 58a2b2c5-66e2bd43@192.168.2.205
CSeq: 101 INVITE
Max-Forwards: 70
Contact: <sip:37683102@192.168.2.205:5060>
Here the client station is at extension 5031 and the mailbox ID is 53371. The voicemail server
should then prompt the caller to enter a PIN and access the voicemail features for the given
mailbox.
A user should also be able to call an external number explicitly from anywhere to retrieve voice
mail messages. When the voicemail server receives such a call, it should prompt the caller to
enter the mailbox ID and then the PIN number. If the user-ID of the voicemail account cannot
be uniquely identified from the mailbox ID or from the called number, the server must first
prompt the user to enter the user-ID before proceeding.
If an EXT-To-DID mapping exists for the calling extension on the line
Note
interface, the user-ID and display name fields of the FROM header are
replaced by the mapped DID number and the display name assigned to
the phone, respectively. In this case, a DIVERSION header similar to the
REFERRED-BY header is also included.

Checking Voicemail from an External Number

The Internet voicemail service provider (IVMSP) may have an external number for their
subscribers to call to check/manage their mailboxes. If this is not available, you may do one of
the following:
• Assign a DID number (from the ITSP).
Linksys Voice System Administration Guide
Advanced Topics for SPA400 Voice Mail Service
142