"I never got your email" sounds like the modern-day version of "the dog ate my homework." But check your junk email folder, and you're bound to see at least a few marketing emails you would have gladly opened.

As email spam filters become increasingly sophisticated, there's a one-in-five chance that the missing email excuse is actually legitimate.

Only 80 percent of commercial email arrived in recipient inboxes in 2017, according to a study by Return Path, which helps companies improve email deliverability. Five percent of email got stuck in spam folders, while 16 percent never even made it that far, blocked at the gateway by email providers.

No email service provider or email marketing expert can guarantee your messages land in the inbox. Essentially, providers promise to deliver your email to the digital equivalent of the post office. But they can't be certain that the mailman (the recipient's email server) will place the mail inside the box. And of course, no one can force recipients to open what they think is junk.

But as an email marketer, you and automation software such as Keap, play an important role in deliverability, too. These strategies, both technical and personal, can help you keep your email out of the spam trap.