Yealink SIP-T40P User Manual page 179

Select the desired account from the pull-down list of Account.
2.
Select Enabled from the pull-down list of Subscribe for MWI field.
3.
Enter the period time in the MWI Subscription Period(Seconds) field.
4.
Click Confirm to accept the change.
5.
The IP phone will subscribe to the account number for MWI service by default.
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.
Advanced Phone Features
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