You can set up your email client in 3 simple steps:
Click on the 'download' button on the browser.
On the screen that appears, select 'Run this program from its current location' and then click on the 'OK' button
You will be shown a screen asking for your Display Name and your Rediffmail email ID.
Go to your Desktop.
Make sure you are connected to the Internet.
Open up your email client
Enter the password of your Rediffmail account when asked in your email client
You will now be connected to Rediffmail and you can download messages.
Alternately, if you would like to configure your email client yourself, you could do so by using the following details:
Incoming Server: pop.rediffmail.com
Outgoing Server: smtp.rediffmail.com
Username: Your Rediffmail username
Password: Your Rediffmail password