One of the main difference between email (besides the obvious) is the fact that your mail carrier doesn't reject mail that reaches your mailbox and they don't sort it into piles for you. Email clients, on the other hand, regularly block emails that come from known spammers and some (like Gmail) sort messages into folders for spam, social media, promotional content, etc.

This difference makes reputation more important for email marketers, since the message won't even reach the mailbox of the target if the marketer's reputation ranking is too low. Though it may not seem like it at times for consumers, email programs remove a lot of spam before it reaches your inbox due to low scores. While business owners have known that their reputation as email marketers matters, recent research suggests that reputation has a more dramatic effect on email marketing than many may realize.

The research in question comes from Return Path, who measures marketers reputation through a metric called Sender Score. According to their website, "Sender Score is a number between 0 and 100 that identifies your sender reputation and shows you how mailbox providers view your IP address. Your Sender Score is like a bank running your credit score to gauge your credit history."

Just as your credit score determines which banks will accept you for loans, a marketer's Sender Score represents the likelihood that marketing emails from the sender will be accepted by certain email providers. Measuring the effect of reputation on email deliverability isn't an exact science. Since each email provider using a different algorithm and each user can enact their own level of spam filtering, it's impossible to know exactly when reputation kept a message from being delivered in opposed to another factor. That said, the evidence is clear that reputation does matter.

Return Path researchers found that one-quarter of email marketers with sender scores between 71 and 80 had their messages landing in spam/junk folders. For those with sender scores between 81 and 90, 10 percent of their messages landed in junk/spam folders.

The data also indicated that things were great for the marketers with best scores. Businesses with sender scores of 99-100 had just 2 percent of messages land in junk folders. And businesses with sender scores of 91-100 have average complaint rates of 0.17 percent, though that's sort of chicken and egg, since their low complaint rate contributes to email deliverability and not the other way around.

"We know that very little legitimate email comes from senders with a Sender Score below 71. But simply having a 'good' sender reputation is no longer enough-it has to be outstanding," said Scott Roth, General Manager, Email Optimization at Return Path. "Marketers need to know that when they send a message to customers, it's going to land in the inbox. Even the difference between 90 and 98 percent delivery is huge. This is precisely why monitoring your reputation and maintaining it at the highest level possible is critical to successful email marketing."

The data from this study also reinforces why it's counterproductive to buy email lists that were not obtained properly. The people on these list will often mark unsolicited content as spam, which will make it harder for legitmate emails from the marketer to go through in the future. An applicable saying in this situation is "The lazy man works twice as hard." Trying to cut corners on creating an email marketing list will end up doing considerable damage to a brand's sender reputation.

According to Return Path, more than half (52 percent) of all messages tallied were from email marketers with sender scores below 71. It is possible to improve your reputation score over time, but the first place to start is with knowing your score.

It's worth it for business owners to periodically check their Sender Score or some similar metric. Email marketers can get a rough idea by checking their open rate, spam complaints, etc. However, since the criteria used varies for each mailbox provider, an outside source is needed to get a more accurate representation of how they're viewed by providers. This can be done through a variety of services, such as, ReputationAuthority, and TrustedSource.

For more news about email marketing, read this article on how email marketing works with Millennial audiences.