3 Rules You Must Break to Expand Your Email Marketing List If building a bigger list is your priority, you'll want to break these traditional marketing practices.

When it comes to email marketing, you can craft the ideal subject line, creative copy and a great offer. But if you don't have an extensive list of active email subscribers to send your message to, nothing else really matters.

How do you expand your email list? What are the rules you should follow?

You can include a "Sign Up For Our Email Newsletter" link on your site, and you can collect email addresses when someone creates an account or makes a purchase. But if you really want to build a larger list, consider rejecting -- yes, rejecting -- some of the traditional practices of email marketing.

Here are three email marketing rules you should break, and explanations for why you should do so:

1. Never use a popup to collect email addresses. Remember the early days of the internet when your monitor would suddenly be flooded with popups, those annoying boxes that seemed impossible to close without a CTR-ALT_DEL reboot? Well, popups are still around, but thanks to popup blockers, people can easily avoid them.

Now, marketers are using a more sophisticated, less intrusive form of the popup: the popover. A popover is a box that appears on a website asking viewers if they want to be added to an email list. These popovers are customizable -- they can be set to appear only after a certain number of page views, only after a certain time period or only with people who haven't visited the site in a set number of days.

Related: The Best and Worst Times to Send an Email (Infographic)

Many companies are finding success with popovers. Patrick Starzan, vice president of marketing and distribution at the comedy video website Funny or Die, says nearly 80 percent of subscribers signed up in response to the popovers the site has been using for more than four years. The popovers appear only after someone has visited at least three pages on the site, and Starzan says he hasn't received any negative feedback about them.

Popovers work best if they're simple, direct and include a bit of humor. So, don't clutter your popover with a lot of words. Keep the language light and fun, and give people a reason to opt in.

2. Always require a double opt-in. Imagine this: You're ready to buy a new iPad Mini. You walk into a store, grab the tablet off the shelf, walk to the register and pull out your credit card. Then, the clerk says, "Before you give us your money, we're going to send you an email. Please open it and click the link. Then, and only then, can you buy this tablet."

Crazy, right? You are ready to buy, but the seller is putting an obstacle in your way. This scenario reminds me of the websites that require people to click a link in an email they have received before they can be confirmed and added to their email marketing list. As my former sales boss used to say, "Stop when they say yes."

Related: How Not to Be a Spammer When Marketing Your Business

Not only does a double opt-in create an unnecessary barrier, but there's also the possibility that the confirmation email won't reach the intended recipient. According to Return Path's Global Email Deliverability Benchmark Report for the second half of 2011, nearly a quarter of all emails never reach their target. Are you willing to take your chances by sending out a confirmation email?

Instead, consider sending a welcome or thank you email to new subscribers after they opt in to your marketing list. The email confirms that the new subscriber's email address is valid, and it also can give people an idea of the type of content they'll be receiving.

3. Never send an email without first getting explicit permission. One of the biggest misconceptions about the CAN-SPAM Act of 2003 -- the first national standards for the sending commercial email in the U.S. -- is that you need permission before sending an email to someone. While the laws in some countries, such as Canada, are changing to require permission, it is still legal to send emails in the U.S. without explicit consent from the recipient.

Rather than require people to opt in, you can give them the choice of opting out. When media company KSL.com added a "group deals" email to its marketing mix, it could have sent an email asking subscribers to opt in to receive it. Instead, it decided to send an opt-out email to give people the opportunity to unsubscribe from the group deals list. It turned out that most people did not opt out. But if KSL had chosen to get explicit permission before adding everyone to the new list, many people might not have taken time to respond, substantially reducing the audience for the group deals.

Related: How to Create an E-Mail Marketing Campaign That People Will Notice