"Do we really have to put an 'Unsubscribe' address in our email marketing?"
This is called an opt-out address. You should definitely include it.
The reason? If an opt-out address is not present, spam filters could wonder about your email. Is it legitimate? Well, he didn't put in a way for readers to opt out if they choose. That sounds spammy to me! Blocked. Not only that, but people like it when you put one in. It shows that you respect their time.
Plus it's required under the federal CAN-SPAM Act
. Your email service provider should have built-in mechanisms for including an opt-out address.