If a subject line gets truncated on its way to your subscriber’s inbox, cautions Mark Brownlow at Email Marketing Reports, it can do more than cause a “wry smile” or a “little embarrassment.” It can cause outright confusion, or it can tell your customers something you didn’t even mean to say. Horrors!

Here’s his advice for avoiding two major subject-line traps:

Remember that any subject line is subject to truncation—even if you never exceed the recommended 50-character limit. You probably account for this limit by frontloading critical keywords, but you might not realize just how frontloaded those terms need to be. “My Yahoo! Mail inbox,” notes Brownlow, “has just 27 characters displayed.” Consider, for instance, how the 50-character subject line Hit it out of the park with iPad this Father’s Day would look if recipients saw only its first 27 characters: Hit it out of the park with. You’ve just lost your product and your holiday theme in one fell swoop. “Perhaps, then, frontloading should mean what it says,” he advises: Make sure you place your hot words “right at the front, not just close to it.”

Exercise caution when using critical “conditioners” in your subject line. “Conditioners are those little extra words or numbers that change the meaning of the words that precede them,” says Brownlow. “There is an important difference between ‘50% off Ice Age’ and ‘50% off Ice Age 3.'” Likewise, he explains, Make Your Neighbors Green With Envy takes on a thuggish environmental tone if truncated to Make Your Neighbors Green.

Frontload, and watch those conditioners. As you write and test subject lines, don’t forget that a lot can get lost in truncation.

Source: Email Marketing Reports.