Yealink SIP-T27P User Manual page 201

To enable subscribe MWI to voice mail via web user interface:
Click on Account->Advanced.
1.
Select the desired account from the pull-down list of Account.
2.
Select Enabled from the pull-down list of Subscribe for MWI.
3.
Select Enabled from the pull-down list of Subscribe MWI To Voice Mail.
4.
Enter the desired voice mail number in the Voice Mail field.
5.
Click Confirm to accept the change.
6.
The IP phone will subscribe to the voice mail number for MWI service using Subscribe MWI
To Voice Mail.
Note
MWI subscription is configurable via web user interface only.
Advanced Phone Features
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