How Does Gmail Determine an Email Is Spam?
Gmail’s junk mail algorithms and user-created forwarding rules are quite effective at auto filtering unsolicited email messages and unwanted junk email, and delivering them to recipients’ junk folders. Unfortunately, there are times when legitimate email messages are marked as junk, even though the subscriber wanted to receive them. Although email services don’t share the exact algorithms for deciding if an email is unwanted by intended recipients, the following are some of the major reasons why email messages may be marked as junk or why rules in Gmail may result in a message automatically being blocked:
Content — Typically one of the least common causes for pushing email messages to the junk box, certain words or phrases found within messages and subject lines can cause them to be caught in a spam filter.
Link sources — If messages include a link to a website that is blacklisted, the messages could be caught in an email spam filter.
Source — If other email messages sent from the same IP address that you use appear to be junk, your emails may be categorized that way, too. In other words, it’s guilt by association. This can become a problem for small email senders who may be on a shared server.
Headers — If there are inconsistencies in the “from” address and “reply to” address and domains, emails will be filtered as spam.
Engagement — Recipients who know how to create rules in Gmail can manage filter settings and deliberately label certain messages as junk email; however, engagement metrics, such as open and click rates, also can affect the email-filtering process.
An increasing number of Internet service providers (ISPs), including Yahoo! and Gmail, are using such engagement metrics to determine if an email should automatically be deleted as junk email, or be blocked or filtered as spam. In effect, Google is simply trying to provide a great user experience, just as Google’s search algorithms do.
So, Google views engagement metrics as an indicator of whether or not the user is interested in email from an approved sender list. We have seen tests where a list with high levels of engagement get through the Google spam filter, while a list without the engagement doesn’t get through.
How to Prevent Email From Going to Spam
How to avoid email spam filters is vital for any marketing or sales team to know. The following are some important strategies and spam filter testing tips to help you get into the inbox of Gmail subscribers and prevent deliverability problems in the future:
Check the email content. If you have a deliverability issue, check to see if the content is to blame. Start by sending a neutral message to a Gmail address using your existing sending infrastructure including the “from” address, sending domain, and IP address.
If it doesn’t get filtered to Google junk mail, break up the copy of the problem email and be sure to send it in pieces to determine if the problem is located in the subject line or message copy. And keep in mind that it could be an image or a link that’s causing the deliverability issue.
Tell subscribers to watch for your email messages. Emails to confirm a purchase or new subscription are among the most opened emails.
So use them to tell your subscribers to watch for upcoming campaigns and to check their spam folders if they don’t receive them. It’s possible users may have created an email rule or spam filter that either blocked or marked your email address and content as junk email.
You may also want to remind your users how to set rules in Gmail: to click the “not spam” link if they find your email address in their Gmail junk folders, which will let Google know that they want to receive your email campaigns.
Ask subscribers to add your “from” address to their Gmail list of contacts. This will help ensure that your emails don’t suffer Gmail automatic forwarding to recipients’ junk folders.
Keep track of your engagement metrics. Do your subscribers open and click your email? Or do they skip and delete your email campaigns without opening them, hit the unsubscribe link, or report them as spam?
Gmail uses such engagement metrics to determine whether its users want your emails. So if your subscribers are inactive — i.e., if they haven’t opened or clicked your emails in a certain period of time, such as 6 months — you should consider running a reengagement campaign. In this way, you’ll identify the subscribers who aren’t interested in receiving your email and can remove them from your email address list.
Make unsubscribing quick and easy. How easy is it for people to unsubscribe from your email list? Is it a simple, one-click process? Is the unsubscribe link easy to find and click?
Do you promptly respond to unsubscribe requests? If people can’t easily unsubscribe, they’re much more likely to report your emails as junk and hurt your email reputation.
Create an opt-in subscription process. In fact, Google recommends using a double opt-in subscription process, which involves sending a follow-up message that each subscriber needs to respond to and click. In addition, Google recommends not using pre-checked opt-in check boxes.
Consider using a dedicated IP address and private domain. This is an important way to help ensure compliance with Gmail’s authentication strategy.
We discussed the important role the IP address and domain name play in email deliverability in a previous feature. And when becoming a “new sender” with a new IP address, be sure to use an IP ramp-up strategy: Start by sending a low volume of emails and gradually increase the volume over several weeks.
Source (& for better understanding):