[linkregister]

I think you're talking about a different use case. The original subject in this thread was about mailing lists that are difficult to unsubscribe from.

I would say (and a legal interpretation of CAN-SPAM would agree) that an unsolicited mass campaign of emails are spam, are not wanted, and aren't legal in the US. A fully individualized, tailored email probably doesn't fall in this class of email.

Double-opt-in is a good email practice. There are several reasons for this.

1. Ensure the email address actually belongs to the account holder. Some people make up an address with a common name instead of using a throwaway email provider, such as Mailinator.

2. Demonstrate to email service providers that the lists are legitimate and aren't used for unsolicited marketing. Many whitelisting and un-blacklisting negotiations are still handled by people. Good practices are important for reputation management.