When you log in to your Adobe account, Adobe occasionally reminds you to add your mobile phone number for account recovery. Once you add the mobile phone number, you can reset your password using a code sent to your mobile phone.
It is not mandatory to provide your phone number. You can reset your password using your email address that is associated with your Adobe account. Adding a phone number, however, provides you the additional convenience of using your mobile phone to reset your password.
If you do not want to add your phone number at this point, click SKIP.

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Your mobile phone number is added to your Adobe account. You can now reset password using your phone.
To change the phone number associated with your Adobe account, see Update your account profile.