We talk a lot about email opt-in here, and you may be wondering "what is a good opt-in definition" or "what is the definition of confirmed opt-in" or even "how does double opt-in work?" (We get all of those questions.) If you are not sure about the exact definition of opt-in when it comes to building email marketing lists or other types of email lists, or the definition of spam, here is a quick review of what each of them mean.
