Do not attempt to open or edit this file in a text editor, as this will likely corrupt the firmware and could "brick" (permanently disable) your phone if you try to install the modified version. Are you trying to recover a locked phone or just performing a routine update Yealink_SIP-T21 E2 & T21P E2_Quick_Start_Guide_V81_20
Regularly updating this firmware is the best way to ensure your office communications stay secure, bug-free, and compatible with the latest VoIP features. What is t21p-e2.bin? This .bin file is the official firmware image for the Yealink SIP-T21P E2 t21p-e2.bin