Flickr Photo: m-cI talk a lot about email marketing campaigns with folks just getting started with email (and you are NOT alone: there are lots of you just getting started). One of the most frequent questions I hear is, "What's the best way to approach subject lines?"

I usually take this question to mean, "How do a I write a subject line that will make people open my message?" But maybe I've been focusing on the wrong question. Maybe the question should translate to, "How do I write a subject line that will compel more people to click through?"

Really, isn't that what you want? Who cares how many people open your email if no one clicks through to take action?

So, how do you write a subject line that will compel people to take action? One crucial piece of standard advice has been to keep it short. All email clients -- Hotmail, Outlook, AOL, Thunderbird, etc. -- truncate subject lines after a certain number of characters, and most of them used to do it after a very few characters: about 40. Now, many email clients allow up to 100 characters, so you can write longer subject lines.

(Note: know your list. If you have lots of domain.com email addresses and domain.com truncates at 50 characters, that should be your limit!)

As it turns out, longer subject lines actually perform better when it comes to click through rates! An interesting report from Alchemy Worx tested 646 subject lines across 205 million messages and found:

• Shorter subject lines (under 6 words) increased open rates for messages
• Longer subject lines (over 11 words) increased click through rates
• Subject lines between 6 and 10 words did not affect open rate OR click through rates

What's the theory? Longer subject lines can convey enough information to speak to a more targeted audience. Fewer people will decide the message is of interest to them, but more of those that open the message will then take action.

Here's an example adapted from the report:

Message A: Your Help is Needed Today

• 1000 people receive the message
• 75% of the list opens it (750 people)
• 5.25% of the list clicks through (52.5 people)

Message B: Donate Now to Save a Cat and a Dog in Flooded Ohio

• 1000 people receive the message
• 35% of the list opens the message (350 people)
• 10% of the list clicks through (100 people)

Even though fewer people open the message, more people click through -- and a much higher percentage of people who open the message click through, drastically increasing the effectiveness of the message overall.

On the one hand, this stuff is hard for me to wrap my brain around; it goes against everything I was taught. On the other hand, I think the numbers are pretty compelling. What's your experience? Have you tested subject line length at your organization?