I want to validate an email validation of type 'abc@xyz.com.com'
Should show an error message if they enter invalid domain name.
Would be very grateful for your help.

You should try matching against this expression to check if valid characters were entered for an email address:

/^[\w\-\.\+]+\@[a-zA-Z0-9\.\-]+\.[a-zA-z0-9]{2,4}$/

Check out the .match() function. I don't want to completely give you the answer on this.

Should show an error message if they enter invalid domain name.

How far do you want to take this? For example, what jwmollman posted does not allow .museum. It does allow .xx which is not a valid extension (yet). I advise to fully read the second linke stbuchok provided. What about arabic domains?

Any budy know about how to perform ajax (email already exist) validation in jsp