Yealink SIP-T4X Administrator's Manual page 166

Administrator's Guide for SIP-T4X IP Phones
5. Enter the period time in the MWI Subscription Period (Seconds) field.
6. Click Confirm to accept the change.
The IP phone will subscribe to the account number for MWI service by default.
To configure subscribe MWI to voice mail 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 the desired value from the pull-down list of Subscribe MWI to Voice Mail.
5. Enter the desired voice number in the Voice Mail field.
6. Click Confirm to accept the change.
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