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10 Tips to Prevent Marketing Emails from Going to Spam

Email Marketing

When you have spent hours crafting the perfect marketing email, the last thing you want is for the message to be consigned to people’s spam folders. But if you have noticed a sudden drop in open rates, that could be what is happening.

Spam filters do an excellent job of keeping the garbage out of people’s primary inboxes. However, the artificial intelligence that powers the filters can sometimes be overzealous, sending genuine emails to the junk folder.

How can you ensure that your outbound emails do not get flagged as spam? Here are 10 tips to help ensure that your marketing emails arrive safely in recipients’ inboxes.

Confirm Opt-In

You should, of course, never send marketing emails to people without their permission. If you do, a high percentage of the recipients will flag your messages as spam, which is likely to get your email address flagged as a sender of spam. The best way to gain people’s permission is to use a double opt-in. The first opt-in is the user providing their email address when they subscribe to a mailing list. The second opt-in is obtained by sending an email asking the subscriber to confirm their willingness to receive emails from you.

Proofread Emails

Spelling mistakes and typos are a red flag for spam filters. Hastily written messages that might look like they have been computer-generated will also trigger some filters. Therefore, take your time crafting marketing emails and proofread them before sending them. If proofreading isn’t your forte, you could ask someone else to check your emails. Alternatively, a grammar checker like Grammarly will check your messages for errors and suggest improvements.

Remove Inactive Email Addresses from Your List

Spammers don’t manage their email lists. Instead, they blindly send messages to as many addresses as they can. As a result, many spam messages are never opened or are sent to inactive addresses. Consequently, spam filters use low open rates and emails sent to inactive accounts to identify spam. The best way to avoid getting flagged by these metrics is to clean up your mailing list and remove inactive subscribers.

Avoid Spammy Subject Lines

In the past, spam filters relied heavily on trigger words in the subject line to identify spam emails. For example, phrases such as “earn extra cash,” “don’t delete,” and “do it today” would send an email to the junk folder. Obvious spam triggers such as these should still be avoided today. But spam filters are more sophisticated now, so you need to consider the subject line in more general terms. In other words, does it sound spammy when you read it out loud?

Abide by the Law

If you break local anti-spam laws, your emails will be flagged as spam, and you could wind up with a hefty fine. In the United States, you must abide by the regulations specified in the Controlling the Assault of Non-Solicited Pornography and Marketing Act, known as the CAN-SPAM ACT. Provisions in the CAN-SPAM ACT include providing a postal address and an opt-out option. The act also specifies that emails must be sent from a genuine person and a valid registered domain name. Local laws will apply if you send emails to subscribers in other countries.

Use the Correct Text to Image Ratio

One of the ways spammers try to avoid spam filters is to put their message in an image rather than text. They do this because images are more problematic for the filters to read and interpret. Consequently, if you send a marketing email containing nothing but a graphic, the message will probably get flagged as spam. Too many images may also have the same result. So, it is best to aim for a content ratio of 80% text to 20% images.

Avoid Using Attachments

You might want to attach a coupon or other marketing materials to an email. However, email attachments can make an email slow to download and are often viewed with suspicion. Furthermore, files attached to an email may trigger anti-spam filters. If you want to provide access to additional files, don’t attach the documents to the email; direct people to a landing page where the files can be downloaded.

Ask Subscribers to Whitelist You

Anti-spam filters generally assume that an email from a contact in the address book is safe. So, asking subscribers to add your email address to their address book or safelist will help ensure your emails get through. Safe listing an email address also sends a trust signal to anti-spam filters, which will reduce the likelihood of your emails being flagged as spam.

Check Emails for Spam with an Email Checker

If you are still unsure why your marketing emails wind up in subscribers’ spam folders, there are online tools you can use to check the spam score of your emails and more. For example, will test the “spamminess” of an email, and will check your email subject line.

Send High-Quality, Valuable Emails

Finally, if you don’t want your emails to be dumped in the spam folder, don’t send spam! As already mentioned, anti-spam filters are getting more and more sophisticated, so they are becoming harder to beat. Consequently, your best way to ensure your email marketing arrives at its intended destination and gets opened is to send genuinely valuable content that your subscribers want to read.


Spam filters work on a scoring system. The more spam triggers discussed above an email contains, the more likely the email will be sent to the junk folder. Failing to follow all the aforementioned tips will not necessarily get your email flagged as spam. Nevertheless, following these best practices will significantly reduce the risk of triggering a spam filter.
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