I was shocked to see that www.spypig.com patents are not found in patent search and my friend patented that procedure as his idea and submitted and received the patent rights.
Now can he send a notice to SpyPig to stop their service? or can he stop further websites like SpyPig?
SpyPig is a email notification system to find whether the recipients read the email or not.
The same way, if someone's idea was copied and patented is that person allowed to send them a notice to stop their service?
The proper way is to notify them in a way that allows you to 'prove' you notified them (a receipt, a witness, etc.). In other words, don't send them an email.
Keep in mind that if they were doing it before you got your patent then you might not be able to enforce your patent against them and they might even be able to invalidate your patent due to 'prior art.'
Getting a patent is one thing. Being able to defend it is quite something else.
Does your friend have the money to enforce the patent through the courts? If not, then practically the patent is not much use.
And what purpose does he have in making them stop anyway? He would be better off offering to sell them the patent perhaps. Or not.
You already said "point taken" when you were told that ideas usually cannot (and shouldn't ) be patented, here: Can I patent something like this? After that, you asked a question that involved you having an idea patented, here: How to sell my idea? Now it's your friend who has an idea patented, and you want to stop a valuable service from operating.
Why do I have the feeling that these are imaginary, theoretical stories?
It would make a lot more sense if you were trying to build a service that adds value to people's lives, and beat competition by offering a better service. There is no point stopping a working solution if you can't make a better one. I think this is pure patent trolling what you are thinking about, and it's no way to start a successful business.