Email Deliverability

How To Avoid Spam Filters (And Keep Your Sender Reputation Intact)

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Is it possible that your emails are being mistaken for spam?

Avoiding spam filters is an ongoing challenge for marketers. The fact is, your perfectly well-intentioned emails can be filtered to spam folders for an ever-growing list of reasons without you realizing it. If left unchecked, sending a high volume of emails that gets routed into spam folders can destroy your sender reputation and force you to hit a hard reset on your email marketing program. 

To help you improve your email deliverability and ensure every message you send lands safely in your recipient’s inbox, let’s discuss what is considered a spam email, and expert strategies for avoiding spam filters.

What is spam, anyway?

Spam is a term used to describe unsolicited, unwanted, or potentially fraudulent emails that are typically sent to a large number of recipients—and it is illegal to send spam messages in many countries.

The U.S. CAN-SPAM Act and Canada’s Anti-Spam Legislation (CASL) provide a thorough breakdown of what is and is not OK to do when sending email, with highlights including:

  • You cannot use false or misleading header information
  • You must give recipients a way to opt out of receiving your emails
  • Your subject line must reflect the content of your email

In September 2021 nearly 89 billion of the 106 billion emails sent were spam—but we can all take a part in reducing the number of spam emails sent.

 If you’re curious, you can learn why we call it spam and how spam has evolved over the years. Otherwise, read on to learn how spam filters work. 

What is a spam filter?

A spam filter acts as a first line of defense for an email recipient and sends potential spam emails to a folder separate from the recipient’s main email inbox. Spam filters generally rely on a mix of technologies including machine learning and artificial intelligence (AI) to identify email messages that contain a virus, include potentially deceptive messages, or come from an untrustworthy sender.

Just a few reasons that a spam filter may intercept an email include:

  • The email includes excessive spammy words or phrases
  • The email design is poor or incomplete
  • The sender reputation is low 
  • The sender’s IP address is blocklisted
  • The email subject line appears spammy, false, or misleading

It’s important to note that a spam filter does not block an email from being delivered, meaning that ESP reports will list emails as delivered even if they were routed to a spam folder. 

This makes it significantly harder for your team to understand your actual success and the best ways to improve your email strategy unless your recipients actively mark your messages as safe. This is another reason why inbox placement rate is the only true measure of a sender’s deliverability—their ability to reach subscribers’ inboxes instead of their spam folders.

How to avoid spam filters

Despite the many challenges of avoiding spam filters, the good news is that they get easier to avoid as you learn more about how to prevent email spam and ways to approach your subscribers with highly personalized and relevant content. That said, the decisions you make early on in your email marketing can have a lasting effect on how successful your program is.

Avoid sending emails that can be considered spam by following these best practices:

Warm up your IP address

If your team is working from an entirely new IP address and email address, then you need to send a low number of emails at first—with 24 hours in between your outreach—and gradually increase the number of emails you send. If you don’t warm up your IP address, then email providers will not have enough historical data to gauge your reputation— and will assume you are sending spam emails. 

We explain how to warm your IP address here for more background. 

Use double opt-in

Double opt-in methods are an essential way to protect your email reputation and recipients. When you enable double opt-in confirmation, someone who signs up for your email communications will receive an email with an opt-in link that they must click before they are officially added to your subscriber list. 

Double-opt-in ensures that everyone receiving your emails wants them, instead of having signed up unknowingly or mistakenly. If someone does not remember subscribing to your emails, then they are more likely to report your emails as spam. 

Double-opt-in also helps you to filter out misspelled or inaccurate email addresses—something that an email checker can also assist with—which will give your team a hard bounce and hurt your sender reputation.  

Brush up on these opt-in best practices to build your email lists the right way. 

Maintain a positive sender reputation

Your sender reputation heavily influences your overall email deliverability. Many factors can influence your sender reputation, including:

  • Bounce rate
  • Feedback loops
  • List hygiene
  • Your email content

Learn more about what an email sender reputation is and learn how to strengthen yours using these expert tips and strategies. We also recommend using a free tool like Sender Score to easily check your IP reputation and track your ongoing sender reputation. 

Get added to address books

The best way to avoid spam filters is to get added to your recipients’ address books—which essentially serves as a VIP pass that ensures you always get access to their primary inbox.

Directly encourage your subscribers to add you to their address books through your email communications. It’s smart to send an onboarding email that explains how they can add you to their address books—with specific instructions for Gmail, Outlook, and other mailbox providers—and you can include consistent nudges in your ongoing outreach to maximize your success. 

Create non-spam subject lines

Your email subject lines are a major factor in whether your emails get flagged as spam or not. While “spam trigger words” are generally considered to be a thing of the past, certain phrases can cause email recipients to manually flag your messages as spam.

It’s best to write email subject lines that give your recipient a clear and honest look at what the email contains. (Remember the CAN-SPAM rules we discussed above?)

A smart way to improve your subject line strategy is to A/B test your messages to learn what type of subject lines improve your open rate and conversions. 

Avoid email firewalls

Email firewalls can block potentially harmful or spammy messages from reaching recipients before a spam filter can even review the email, because email firewalls rely on sender reputation scores to decide whether to block a message. If your email recipients continue to report your emails—either because they do not remember signing up for your emails, you reach out too frequently, or your messages fail to provide value—then your sender reputation will plummet and email firewalls will stop your messages from being delivered. Keep in mind that each email provider will have different firewalls in place, meaning your messages may deliver to an Outlook inbox but get caught by Gmail’s firewall. 

Monitor complaint records

As explained above, email recipients can report your messages. If too many people report emails coming from your address, then you will receive an automated warning email. Monitor for these types of messages and immediately stop all outreach until you understand what may be causing an increase in your abuse reports. If you fail to lower your abuse reports, then you risk being blocklisted from sending emails entirely.

Don’t buy email lists

It can be tempting to purchase email lists to jumpstart your email marketing or in hopes of driving an immediate boost in sales. Don’t do it. Purchasing an email list is never a good idea, and it directly contradicts the best practice of earning subscribers who opt in to receive your messages. 

Email lists purchases from third-party vendors nearly always include incorrect or outdated emails and spam traps that can seriously hurt your sender reputation, regardless of how successful your program has been in the past. Sending emails to recipients that did not ask to receive your messages is a guaranteed way to increase your spam complaints and hurt your brand reputation—would you appreciate it if someone you didn’t know reached out to you trying to sell you something? 

Manage the frequency of emails

People receive an overwhelming number of emails every day, and you want them to feel excited when they see a message from your brand. Limit how frequently you reach out to your subscribers to be respectful of their time and busy lives. We recommend you empower recipients to customize how often they hear from you through a preference center that allows them to opt in and out of your email streams and select a daily, weekly, monthly, or quarterly outreach cadence. 

Clearly explain each of your email streams and allow your subscribers to opt-in and out of those streams in a convenient way. While it may be discouraging to see your total number of subscribers go down, it’s important to focus on reaching high-quality subscribers that will engage with your content. 

Monitor your inactive subscribers

Closely related to the above note about the frequency of your outreach, your team should regularly monitor your inactive subscribers and adjust your outreach timing, cadence, or strategy to re-engage them. If subscribers do not engage with your emails for more than a month, you should reduce how often you reach out. After three to four months of disengagement, a re-engagement campaign may win them back. If the recipient continues to not engage with your emails, then you should remove them from your outreach.  

Avoid attachments

Email attachments often cause email deliverability issues because they increase the email size and face greater scrutiny from mailbox providers looking for potential viruses or malicious content. If you are hoping to send a file or supplementary content, we encourage you to create a landing page for that content or include it within a blog post that you link to within your email. Or, you can upload your attachment to a Google Drive or Box folder that you link to within your email (just be clear about where the link will take your subscribers). 

Optimize email images

Image-heavy content has a higher likelihood of being blocked by spam filters—or your images may be disabled by your recipient’s email provider. Be sure to optimize your images to be a smaller file size, and include alt-text for each image you include. Test your emails across different email providers to ensure your email appears how you intend. In general, you should strive for an 80/20 split for your text-to-image ratio. 

Segment your outreach lists

One of the core ways to avoid spam filters is to consistently approach your subscribers with highly personalized and relevant content tailored toward their needs. Segment your subscribers based on their demographic information and past shopping behavior to approach them with emails that enhance their experience and make their life easier. 

Ensure every email lands in your recipients’ inboxes

The best way for email marketers to avoid spam filters and negatively affect their spam score is to become deeply versed in how spam filters work and the best way to engage your unique communities—which is much easier said than done.

While specific email elements like attachments, subject lines, and body copy can cause your emails to be mistaken as spam, there are other behind-the-scenes considerations like your sender reputation that will largely dictate your ability to reach your subscribers in meaningful ways.

To help you improve your email deliverability and gain crucial insights and guidance for your team to reach more people and increase engagement, read “The 5 Minute Guide to Email Deliverability.”