Single versus Double Opt-in
Double Opt-in means that whoever subscribes your newsletter needs to confirm their subscription. That's typically ensured by sending an email to the "new subscriber" with a link to activate the subscription. If the subscription is not activated you won't send newsletters to that address, who becomes an inactive subscriber. This 2-steps method demands for more engagement from your subscribers than the Single Opt-in where you don't send a confirmation email or that email is just informative (the new subscriber is already active, although you provide instructions on how to unsubscribe).
Everyone using mass email marketing tools aims at high delivery rates and high market response. To achieve these results you must focus on building a high quality mailing list which ultimately means having people interested in your products, services, news, etc. In fact, people who really care for what you have to say are likely to be more proactive.
Pros and Cons
Not so long ago many people discovered the benefits of mass email campaigns. Sending emails was apparently free and easy: all you had to do was to collect emails addresses and build a large base of subscribers. That was specially attractive for entrepreneurs, start-ups and small businesses (who are usually eager to enlarge their consumer base) but also to large companies who were thrilled with this new "free" mass marketing tool. From low-budget homemade strategies (which included collecting email addresses randomly from the cyberspace) to highly sophisticated viral campaigns (where someone would end up entering her email address) the spectrum of initiatives was very wide.
But then many people realised - unfortunately not all people - that to be effective email wasn't that free and easy to use.
You have to have your emails delivered - that means having a good email service that passes anti-spam filters and reaches your targetted inbox. Technically that also means your email servers have a good reputation (i.e. they are not blacklisted as spam servers) and your message (format and content) complies with anti-spam filters. If people mark your emails as spam or if your mails bounce back (because the address isn't valid or no longer exists) you are creating a bad reputation and that can frustrate all your communication efforts. And then, of course, you need a system that can send a large number of emails in minutes - that's also not that free and easy to accomplish as you might have experienced.
In this context you easily realise that Single Opt-in can be a big problem.
Embracing the Double Opt-in
We share the view that good email campaigns must be built on sound ground and that means focusing on quality rather than quantity. That's why we adopted a Opt-in policy for our Newsletter Service. As we serve a large number of clients we can't take any changes, so can't let a "poor quality" mailing list put at risk our entire service reputation and endanger quality of service for other clients. That might mean that your database will grow at a slower pace but also means that you are in fact communicating with real people who are really interested in what you have to say.
We are aware that some special cases arise and some real-life situations require special treatment. So in some cases you can add email addresses manually and the system won't send any activation email. However, whenever a subscriber uses the subscription form embedded on your website or whenever you use the bulk import tool (because, for instance, you are migrating from another system) we always send a activation email.
Final note: we don't share your database information with anyone and we charge our clients based on their database size.