Author: Spam Resource
Description:
An article addressing what double opt-in means, how it works and why you shouold do it.
Different names for the same practice.
Whether you call it closed-loop opt-in, confirmed opt-in, verified opt-in or double opt-in, you're generally referring to an email address verification process used to validate an email address before adding it to an electronic mailing list. Double opt-in is something of a misnomer, because it's not a second opt-in; it's address verification. However, what you call it is less important than whether or not you employ it.
Why should you do it?
You do it to prevent forgeries. The process nearly eliminates spam complaints, and any you do receive can usually be easily disproved.
It can also ensure better deliverability. If you send email, you know how many spam filters (both good and bad) there are out there. They will filter or block even confirmed opt-in email. Why they do is a whole other issue, but if you can demonstrate that you correctly utilize double opt-in, you can get whitelisted by various spam filtering organizations and companies.
How does it work?
Generally, it starts with a web form. A potential recipient will sign up for emails by entering their email address into your form and clicking the submit button. What happens next is they are sent a confirmation request email. In that email, there is a unique coded URL that the recipient clicks on to verify their identity. If the recipient does NOT click on the URL, nothing happens. They are not added to your list, and you don't email them again.
A mailer does it to prevent forgeries. The process nearly eliminates spam complaints, and any you do receive can usually be easily disproved.
If you decide to implement this process on your own, make sure you keep records of all the opt-in requests and completions. IP addresses, opt-in codes, etc. Also, make sure your confirmation method can't be spoofed. Any validation URLs should have a coded URL, not a plain URL that contains the person's email address.
Article Source: http://www.spamresource.com/2003/05/double-opt-inconfirmed-opt-in.html