General settings for IMAP configuration
While adding a new account, select IMAP
Enter Your Name, (enter your name exactly as you want it to appear to recipients.)
In the E-mail Address box, type your e-mail address.
In the User Name box, type your account name.
In the Password box, type your password.
Specify incoming server name as imap.rediffmailpro.com and port as 143
Specify Outgoing mail server (SMTP) as smtp.rediffmailpro.com and port as 587
Make sure that you have checked Outgoing Server Authentication