Send VErification email using Zoho Form

Hi,
I know "send mail" allows us to send email.
I am able to send mail to the email that has been entered into the form.
So far so good..

I would like to use some Random number function in the message ( as verfication code)
so that the person has to enter a valid email id inorder to reccive that verification code.

Can anybody please help me with this.
Thank you,
Regards

Deepa