There are a million and one tips out there on how to write more effective marketing emails, but even if you spend hours using all this advice to carefully craft the perfect message, you're still probably getting ignored a lot.

Don't feel bad. Even some of the web's best known email marketing experts end up with a lot of unopened email.

Take AppSumo and SumoMe founder Noah Kagan, for example. He's built a large chunk of his business around attracting more eyeballs to the great stuff his fellow entrepreneurs are building and he still manages open rates of only around 30 percent.

Double opens

Hey, that's great, you might say--that's what I'm doing and I'm super satisfied with it. But Kagan isn't satisfied with 30 percent or thereabouts. On his blog he shared a super simple trick he learned from Easybib co-founder Neal Taparia which allows him to increase this initial open rate by 30 percent. Here's what it entails:

  • Step 1. Take the same email you sent and change the subject line to something new;
  • Step 2. Email it out a week later just to your non-opens

Yup, that's it. And despite this trick's being mind-blowingly easy, the results, Kagan writes, speak for themselves: "11% more total opens so far which is 30%+ more opens than if I did nothing. One minute of work = 7,028 more people read my email."

Now he wants other founders to give this idea a try and he's setting a little "homework" to nudge them in that direction. "If you've sent an email to your list in the last four weeks. Go into your email software, and re-send to the un-opened subscribers," he suggests.

Doubling up in other areas

It's a simple and effective idea for email marketing, but on the Customer.io blog, iDoneThis founder Walter Chen suggests the principle of getting over your fear of bombarding customers and reaching out to them more than once can actually pay dividends in a variety of business contexts.

"When a potential customer's trial is about to expire, you don't just send a single email and pray that they'll notice it and put down their credit card to convert. You email them a sequence of emails with increasing urgency that their trial is about to expire that stops when the customer converts or the account gets cancelled," he offers as an example. Apply this principle of multiple approaches as broadly as possible, Chen advises.

"It only takes a couple of minutes to add a few variations to your lifecycle emails, and you get massive results," he concludes. Just don't overdo it and resend every email or confuse customers by altering your message with each contact--all you're trying to do is rephrase your offer to get the attention of a new segment of customers. Don't muddy the waters by appearing to alter what you're offering every week.

Are you going to give "double opens" a try?