Hello sir, I am Ranjeet. I am from Mumbai. I want you to help me by giving me some information about the Squirrel mail service at Indian Institute of Technology (IIT) Bombay. Can you help me?

Centralized Email facilities at IITB provide a WEBMAIL system as well as a IMAP server. It is based on open source software.
Under the WEBMAIL system there are two alternatives:
SquirrelMail and
IlohaMail

As you have asked about the Squirrel mail service at Indian Institute of Technology (IIT) Bombay, I am giving you information about it, check below for the details

SquirrelMail is a standards-based webmail package written in PHP.
It includes built-in pure PHP support for the IMAP and SMTP protocols, and all pages render in pure HTML 4.0 (with no JavaScript required) for maximum compatibility across browsers.
It has very few requirements and is very easy to configure and install. SquirrelMail has all the functionality you would want from an email client, including strong MIME support, address books, and folder manipulation.

SquirrelMail is also highly customizable.
The systems administrators can write, install, and share "plugins" at the SquirrelMail server to extend its functionality to meet your organization's needs.

Because of the high level of customization available to the organization with SquirrelMail, some of the items in this manual may not apply.

Some SquirrelMail installations, but not all, allow a user to change their password through the web interface.
If this is a feature you need, but don't have, contact your administrator.