What is considered a proper unsubscribe link to google?


I was reading this from gmails bulk sender guidelines:

"A user must be able to unsubscribe from your mailing list through one of the following means:

Make sure recipients can unsubscribe through either:

A prominent link in the body of an email leading to a confirmation page, without requiring recipients to provide additional information

An option to reply to your email to unsubscribe"

At present I have people go to the unsubscribe page where they have to enter their email and click unsubscribe, which is what a lot of newsletters and mailings have. But I am wondering if this is a violation of their guildeline that the user shouldn't have to enter any information (in this case their email).

My concern with having auto unsubscribe links is what happens when people forward the emails and then someone else clicks the unsubscribe link? Won't the forwarded person unsubscribe the original subscriber?