Did you enable E-mail on Status Change in your account settings?

Yes. Email on Status change is enabled

Apologies. Product version is 2.1.0 not 2.1.3

Rinu George,

I was not able to reproduce your problem with a fresh install of the latest stable MantisBT release (2.8.0 at the moment).

I recommend that you upgrade to the latest (download from [1]). If after doing so the problem persists, provide detailed step-by-step instructions to reproduce the issue; the following additional information may also be useful:

• Exact version of PHP, Database, Web server, Browser and Operating System
• Relevant customizations (e.g. changes in config_inc.php, etc)
• Installed plugins or custom functions ?
• Was the MantisBT source code modified in any way ?

[1] http://mantisbt.org/download.php

Changed View Status to public as I see no reason to have it private.

For defining the new status, I have defined them in below files. Have I missed out any?
config_inc
config_defaults_inc
custom_constants_inc
custom_strings_inc
strings_english.txt

I have defined them in below files.

This is not enough information to try to reproduce the issue.

Have I missed out any?

No, but you changed some files that should not be changed

config_defaults_inc

You should never change this file, any configuration should be done in config_inc.php

strings_english.txt

You should never change this file, any message related configuration should be done in custom_strings_inc

You provided hardly any of the informations requested at 0023682:0058278
I will resolve the issue as "Unable to reproduce" if you don't provide step by step instructions how to reproduce the issue on a clean install of latest stable version (2.9.0 at the moment)

Furthermore you should check your web server and PHP logs for errors and warnings.