d321 flash file Download on your Computer. Firmware comes in a zip package, which contains Flash File, Flash Tool, USB Driver and How-to Flash Manual.
Micromax d321 firmware Readme Once:
[*] Take a Backup: If you are going to flash the above Firmware on your Micromax D321 device, then take a backup of everything as because your personal data will be deleted after flashing the stock firmware.
[*] The firmware shared on this page is officially released by the company and helps you to recovery your device if you ever got bootloop, software error, update error, hanging and dead issue.