HTC One is on display at a store. (Reuters)Reuters

A new CM12.1 series custom ROM has been made available to HTC One M7 by the prolific mobile firmware developers, Cyanogen.

This news certainly brings cheers to the 2013 HTC flagship smartphone owners since the company has disbanded future software support for the One M7.

[Read more: HTC One (M7) Software Update Service Ends with Android 5.0.2 Lollipop; Don't Wait for v5.1 Stability Software, Says Company]

With the release of new CM12.1 custom ROM, HTC One M7 users can explore the new email app powered by Boxer. It boasts of multiple account support, exchange support and canned responses for quick replies.

Other customisations options include sound alerts (bells or whistles), option to select different LED colour display for email notifications and many more and also come with bug fixes to previous v5.0.2 OS.

For the uninitiated, the new CM12.1 series CyanogenMod custom ROM is around 257MB in size and is based on the official AOSP (Android Open Source Project) 5.1 Lollipop OS.

Prerequisites (Things to remember before installing the CyanogenMod CM12 Nightly):

1.  Make sure the device is rooted before going forward with the custom ROM installation

2.  This new CyanogenMod CM12.1 Android 5.1 Lollipop custom firmware has to be installed on the HTC One M7 model only ; if tried on other devices, it might get bricked [To check your device model: Go to Settings >> About phone >> model number]

3.  Installation of custom ROM requires clearing of memory in the smartphone, so make sure to back all the data by installing Clockwork Mod (CWM) Recovery/ TWRP in the smartphone.

4.  Users make sure you have installed USB drivers on the PC, or else your smartphone (HTC One M7) will not be recognised by the computer.

5.  Make sure your device has more than 80% battery, or else there is a chance of smartphone getting temporarily bricked if the installation process is interrupted mid-way.

[Disclaimer: This procedure is very technical and should be performed by a person with sound knowledge of rooting (or manual software installation) Android devices. If the step-by-step installation process is not followed properly, there are chances of the smartphone getting bricked or being permanently irreparable. IBTimes India cannot be held responsible for any damage or claims from readers if the procedure does not yield the required results or if the smartphone is bricked. Hence, users are advised to proceed with caution.]

Tutorial: Step-by-step Installation Guide for CyanogenMod [Official] Android 5.1 Lollipop CM12.1 custom ROM on HTC One M7 (GSM) model:

Step 1: Download CyanogenMod [Official] Android 5.1 Lollipop CM12 custom ROM (HERE) and Google Apps (HERE/HERE/HERE) in to your PC.

[Note: build-release date - 26/04/2015]

Step 2: Connect HTC One M7 to PC via USB cord.

[Note: Before plugging the phone to the computer, be sure that you have installed USB driver software, if not, click HERE to download the firmware]

Step 3: Then, place Android 5.1 Lollipop zip file and Google Apps files into the phone's SD card memory. [Note: Users are advised to paste the .zip file in SD card root, not in any other folder.]

[Note: Before installing the custom software, be sure that the device must have been rooted and has installed ClockworkMod Recovery tool.]

Step 4: Later, place boot.img file in to the android-sdk-windowsplatform-tools directory.

Step 5: Now, turn off the device and disconnect from the PC.

Step 6: Perform the regular Bootloader mode sortie, by press holding 'Volume (Down)' and 'Power' buttons.

Step 7: After entering the Bootloader mode (on the phone), go to android-sdk-windowsplatform-tools directory (on the PC) and open Command prompt, then type in: 'fastboot flash boot boot.img' and press enter.

(To enter Command prompt: Shift + right-click >> open Command Prompt)

Step 8: Then, type - 'fastboot reboot' and press enter. Then, follow instructions displayed on the screen. Select BOOTLOADER option to enter Recovery Mode.

Step 9: After entering the Recovery mode, clear the phone memory, by choosing 'wipe data/factory reset' [Note: use Volume keys to navigate and power button to select options, while operating under Recovery Mode]

Step 10: Now, clear the cache memory by selecting 'wipe cache partition'.

Step 11: Then to go back to ClockworkMod recovery, and select 'advanced' and tap 'wipe dalvik cache' [Note: This step is optional, but many recommend this procedure so that user will not face boot loops or any other errors in the middle of custom ROM installation]

Step 12: Again come back to main recovery screen and then tap 'install zip from SD card'

Step 13: Then tap 'choose zip from sdcard' and go to Android 5.1 Lollipop ROM .zip file in SD card and enter the installation process. Repeat the same procedure for Google Apps [Note: use Volume keys to navigate and power button to select options]

Step 14: Once done with the installation process, navigate to '+++++Go Back+++++' and re-start the device by opting 'reboot system now' seen in the recovery menu.

Now, your device (HTC One M7) will take a few minutes (only for the first time) to complete the booting process.

Head to Settings >> select 'About phone' to confirm the installation of Android 5.1 Lollipop custom ROM.

[Credits: CyanogenMod.Org]