how to reject INVITE from unknown sources

[Yealink Support]

Hi all,
Do you mean you just want the phone to accept the message only from PBX?
If you are using our latest T2X V71 firmware or V70 firmware, please use below auto provisioning parameter to enable this feature.
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#!version:1.0.0.1
account.1.sip_trust_ctrl = 1
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#account.1 means that it takes effect in account 1.
If you are using V61 or V60 firmware, please use this parameter:
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[ account ]
path = /config/voip/sipAccount0.cfg
SIPTrustCtrl = 1
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