The question of single vs double opt in for list building is one that has been around for what seems like forever. It’s almost on a par with whether the chicken or the egg came first and – like that conundrum – there’s no consensus on the correct answer.

Single opt in means that your potential list member just has to take a simple action such as putting their email address into a box on your site and pressing a submit button of some sort.

Double opt in means that they have to do the first action (naturally, otherwise they wouldn’t stand a chance of getting on your list at all) and then they have to click a confirmation link that – hopefully – doesn’t get sent to their spam folder.

So, which method is better?

If you want more people to be on your list, single opt in is better – the less steps there are to something happening, the more likely it is to happen.

If you want to protect yourself from possible spam complaints, double opt in is better. This is the “selling point” for double opt in. No-one gets onto your list unless they click a link from a message that gets sent to their email account. So, unless their email account has been hacked, you’ll only get people on your list who have a live email account that they check. So you should get less spam complaints and a higher readership of your emails.

Of course, theory is good.

But does this work in practice?

The glib answer is that you’d need to test for yourself.

But there have been some tests run by other people and they confirm what you’d expect in that less people complete the second step of confirming their email address.

One test I read recently went so far as to track how much money was spent per subscriber and they found that double opt in subscribers tended to spend more money once they were on the list.

But, before you get too excited, that was outweighed by the larger number of single opt ins who on average spent less money but made up for that by the greater number of them. So the overall “take” was higher with single opt in.

The autoresponder companies such as Aweber keep track of spam complaints and if your spam rate is too high they will warn you and could even remove you from their service.

So you definitely have to watch the spam complaint numbers.

But I suspect (I’ve not done any testing on this, so I could be wrong) that the spam complaint rate is mainly dependent on your email subject line and possibly the content of the email itself (although I personally think that’s less of an issue).

If it’s been a long time since you last mailed people, more of them will have forgotten about you and that could increase spam complaints. But that would be the same whether or not people had taken the extra step to opt in initially.

For near enough all my email lists, I use single opt in.

I know that personally I’m less inclined to click a “subscribe” link and I’m not completely convinced that the average potential subscriber will care enough to click a link. Again, it’s down to testing if you want to really work out what’s best for you.

The other thing to remember is that a lot of people use more than one email address.

Sneaky but true.

I certainly use more than one email address so that I can easily filter out spam and I know I’m not alone in that. So if I don’t “trust” an offer, I’ll use one of several semi-disposable email addresses that I have and then only properly subscribe if I actually want the emails.

And probably the best advice I can give on the decision between single or double opt in is to try it for yourself.

Go with your gut reaction and then do a few tests.

And remember that what is the best way today may not still be the best way in a few years time, so go back and re-test every now and then!