Yealink SIP-T21 - Manual (Page 123)

Advanced Phone Features
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will be indicated in three ways: a warning tone, a prompt message (including a voice
mail icon) on the LCD screen, and the MESSAGE key LED illuminates solid green. This
will be cleared when you retrieve all voice mails or delete them.
The MWI service is unsolicited for some servers, so the SIP-T21P/SIP-T21 IP phone only
handles the MWI messages sent from the server. But for other servers, the MWI service
is solicited, so the SIP-T21P/SIP-T21 IP phone must enable subscription for MWI.
Note
The MWI Subscription parameters you need to know:
Option Description
Subscribe for MWI Enable or disable a subscription for MWI service.
MWI Subscription Period
Period of MWI subscription. The IP phone sends a
refresh SUBSCRIBE request before initial SUBSCRIBE
expiration.
Subscribe MWI to Voice
Mail
Enable or disable a subscription to the voice mail
number for MWI service.
To use this feature, you should configure subscribe for
MWI and the voice mail number in advance.
Note
To configure subscribe for MWI via web user interface:
1. Click on Account.
2. Select the desired account from the pull-down list of Account.
3. Click on Advanced.
4. Select Enabled from the pull-down list of Subscribe for MWI field.
MWI service is not available on all servers. Contact your system administrator for more
information.
Whether the phone sends SUBSCRIBE messages for MWI service to the account or the
voice mail number depends on the server. Contact your system administrator for more
information.