Email marketing can be easy to understand but hard to master. While it's easy to understand the idea of sending marketing information to past and potential customers, it can be challenging to craft an email marketing message that accomplishes those goals. A recent study from Return Path offers some insights on how the email filters on Gmail affects how consumers interact with emails.

In case you're one of the relatively few people who have never used Gmail, a quick explanation is necessary. Most emails have an automatic spam filter, that blocks messages from known spammers and filters messages that are likely to be spam into a separate folder from the regular inbox.

Gmail's filter goes a bit further and besides the spam folder, it also filters an inbox into regular messages, messages from social media platforms and promotional messages from retailers. While this certainly makes things easier for the mailbox users, it also means that many messages from business owners and marketers may be missed.

The Return Path email marketing solution has a feature that allows marketers to see how their messages were categorized by Gmail. Using data from Return Path's Consumer Network of nearly 2 million active inboxes, researchers were able to find certain insights into the impact of Gmail tabs on subscriber engagement.

The sad truth the researched revealed is that if a message ends up in an alternative tab, the likelihood it will be read drops considerably. The lion's share of people check their regular email box multiple times a day, but not so with the tabs. According to Return Path, just a little under half (45 percent) of tabbed inbox users check the Promotions tab at least once each day.

The report also found some evidence that Google might be a little overzealous in the way they categorize messages. They found that Gmail's automatic sorting feature is proving less than effective, with one in 10 users reporting incorrectly categorised messages.

"Reaching the inbox is critical in today's competitive marketplace. And in the case of Gmail, it's just as important that messages are delivered to the expected category," said Cody Bender of Return Path in a statement on the new research. "Gmail has created the industry's most sophisticated email sorting system, so it's vital that marketers pay attention to how their messages are being classified."

There are things that business owner can do to ensure that messages get placed in the highest inbox level. The best option is to recommend that email subscribers add the retailer's email to the safe sender list. Gmail also has a feature where people can move an email to a different folder, which should tell the email client that the user considers that message to be important.

Besides relying on the email user to properly sort the email on their own, there are some other precautions business owners can take. Email servers classify mail based on the domain of the email address, the subject line and the contents of the email (e.g. html structure, attachments, etc.). Here are a few ways marketers can use that information to prepare better campaigns:

Avoid using "$" and "%" in the subject line of message if you want to avoid having it go into the promotions tab or in the spam folders. Messages that contain dollar signs or percentage symbols are almost always spam or marketing messages from a retailer.

Only send emails to people who subscribed to a list. When a person clicks the "Mark this message as Spam" or a similar button on their email client, it sends a message to the email server and it serves as a mark against your domain. If you get too many of these, your messages may end up in the spam folder or blocked altogether.

The takeaway from all of this is that business owners and marketers can't just slap together whatever they want and expect it to be effective. A message may not even get seen if it's not good enough to pass through the mail filters on Gmail or other mail servers. It's not an impossible challenge, but it's important to be aware of the situation and to plan accordingly.

For more data and tips on email marketing, check out this article to learn more about how domain reputation matters for email marketing and what marketers can do to stay on the good list.