Yealink SIP-T21 - Manual (Page 130)

User Guide for the SIP-T21P/SIP-T21 IP Phone
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Why can’t I send a SMS to any other phone?
SMS depends on support from a SIP server. Contact your system administrator for more
information.
How to change the user password?
To change the user password via web user interface:
1. Click on Security->Password.
2. Select user from the pull-down list of User Type.
3. Enter the new user password in the New Password field and Confirm Password field.
4. Click Confirm to accept the change.
Note
How to make a call using SRTP?
You can enable SRTP to encrypt the audio stream(s) of phone calls. The parties
participating in the call should enable SRTP. You can enable SRTP on a per-line basis.
To enable SRTP via web user interface:
1. Click on Account.
2. Select the desired account from the pull-down list of Account.
3. Click on Advanced.
If logging into the web user interface of the phone with the user credential, you need to
enter the current user password in the Old Password field.
User password is configurable via web user interface only.