I have downloaded one of your form, which is working perfectly but I am getting mail as jotForm, how can i change it according to my server

If I understood you correctly, you are referring to the notification emails that are being sent to you when submissions are being made on your form. Yes, you can use a custom Sender Email instead of our noreply@jotform.com options, by following this guide:

http://www.jotform.com/help/238-How-to-Add-a-Custom-Sender-Address-to-an-Email-Alert

You will be able to send notifications with your custom sender email address.

Similarly to the above, you can even send notifications through your own SMTP server:

http://www.jotform.com/help/244-How-to-Setup-SMTP-for-a-Form

Both of the above methods will ensure that the recipient sees your address as the sender, and not JotForm.

Please let us know if you need any further clarifications or assistance, and we will be happy to help.