Yealink SIP-T2 SERIES Administrator's Manual page 688

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
To configure server redundancy for fallback purpose via web user interface:
1. Click on Account->Register.
2. Select the desired account from the pull-down list of Account.
3. Configure registration parameters of the selected account in the corresponding
fields.
4. Configure parameters of SIP server 1 and SIP server 2 in the corresponding fields.
5. If you use outbound proxy servers, do the following:
1) Select Enabled from the pull-down list of Enable Outbound Proxy Server.
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