>> What's the source of the email?
It's an email forward, who knows what the source is. That's irrelevant to the point of the page.
>> Was it spam mail?
Most likely yes. If not it would have been specified. The site is best known for debunking urban myths and email forwards.
>> How many people do they think received these kind of emails?
Ask them. Is it relevant? I'd imagine they only debunk/verify emails that are widespread enough to get attention outside of being forwarded or that are specifically requested or of interest. An item existing in snopes is not a comment on the relevance of the subject.
>> Why was it considered a rumor?
Who said it was a rumor? They are attempting to verify or debunk a claim.
>> What I argue is the fact most of what that website does is fake rumors.
Why do you think that? Just because you haven't been exposed to the urban myths, email forwards, or other claims it researches doesn't mean they're fake. Please provide an example of an item you think is fake?
>> It's the worst kind of "rumors".
The site is intended to be a fact-checking resource for people to look up claims they've heard or read and get information that verifies or refutes those claims. It is not like they make stuff up just to debunk it. People generally go to snopes with a subject in mind to look up.
I still think you're confused about the site, otherwise I simply don't understand your objection.