Double Opt-In, basically, is this: Joe signs up to your newsletter/mailing list – your autoresponder sends Joe an email with a confirmation link.  Joe needs to click on this link before he is officially added to your list and gets whatever he was signing up for.  If Joe does not click on this link, he will not get any email from you because he will not be a confirmed member of your list.

Double Opt-In means that a person must confirm that they want to be on your list, want to receive emails from you, and want whatever it is that you are offering.

It is a great way to protect you from bogus SPAM complaints (if they confirmed their subscription by clicking on the link, they obviously signed up for your list and it can’t be seen as spam), and it also makes for a more responsive list.

I personally will not build any list unless it is double opt-in – and I don’t think you should either. 

By requiring your subscribers to take an additional step to get on your list, you ensure that they really do want to be on your list.  This makes for a more responsive mailing list, and this equals more profits for you.

Some people will argue that by forcing people to take the extra step to sign up to the list, you are losing people that could become customers in the future.  My take on it (and this is shared by many other people I have talked to) is that if they can’t take an extra few minutes to wait for the confirmation email to come and click on that link – is this really someone you want on your list?

They will probably never buy anything from you, and will do nothing except inflate your subscriber number.

I would highly suggest that you use Double Opt-In – you’ll get a more responsive list, you’ll be able to protect yourself against bogus spam complaints, and you can focus your time on people who really want to be on your list.

Using Single Opt-In is just not a good decision, in my opinion.