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How to Avoid Spam Filters

Marisa Sanfilippo
Marisa Sanfilippo Contributing Writer
Updated Dec 11, 2020

To make the most of your email marketing efforts, you must find ways to keep your messages out of your customers' spam folders.

No matter what kind of business you have, email marketing is a great way to connect with your audience. When used correctly, email marketing can have a huge return on investment, but it only works if your audience actually sees your messages. All too often, email marketing messages get sent directly to spam folders, where they are unlikely to be seen. However, there are steps you can take to ensure your emails end up in your recipients’ inboxes rather than being lost forever in their spam folders.

What is spam?

To fully understand how to avoid the spam filter, it is important to have a clear picture of what spam is and how spam filters work. Put simply, spam is an email that the recipient doesn’t want or didn’t ask for.

Spam messages account for almost 54% of email traffic, according to research from Statista. However, this figure actually represents a decrease in overall spam volume. This data reflects what you may typically think of as spam: unsolicited emails, phishing scams and emails sent without consent.

When it comes to legitimate marketing emails, like the ones you’re hopefully sending, nearly 85% are making their way into consumers’ inboxes. Of course, that means 15% are not, and these messages may even be hurting the senders’ chances of getting into inboxes in the future.

What qualifies as spam?

Your email becomes spam to someone as soon as it’s overwhelming or irrelevant. Are those the technical or legal benchmarks? Of course not, but in the real world, where you want to generate leads or make sales, that’s what you need to be thinking about. Relevance and permission are everything.

Why does it matter if you annoy those people you’re emailing? Because, if you do it often enough, they are likely going to mark your emails as junk or report them as spam instead of just deleting them, because it’s often easier than unsubscribing. Even if you have the “unsubscribe” or “manage your account” links posted in every email, some people will report or flag you as spam just for annoying them.

What are spam filters?

Spam filters vary among email providers, but they are essentially automated gatekeepers that use a predefined set of criteria designed to determine the likelihood that an email message is spam. 

The filters work by reviewing specific criteria, and these criteria and the weight assigned to each requirement can vary dramatically from one email provider to the next. To make it more difficult to game the system, providers change the criteria regularly. Nonetheless, there are some steps you can take to give your emails the best chance of getting to inboxes.

How to prevent your emails from going into the spam folder

Your emails don’t have to be destined for spam folders. Here are some tips to ensure your messages end up in recipients’ inboxes:

Write a good subject line.

An email’s subject line plays a huge role in whether it gets sent to spam folders. Keep these things in mind when crafting your subject line:

  • Capitalization: Don’t use title case. Your subject line isn’t the title of a blog post, the name of a song or the title of your first book; it’s a sentence designed to pique the curiosity of your readers and encourage them to see what’s inside your emails. A well-written sentence doesn’t capitalize every word. When you use title case, there is a good chance your email will be sent straight to a junk folder.
  • Punctuation: Your subject lines aren’t texts to your best friend. Using several exclamation points or question marks is likely to raise red flags. Including more than four will almost certainly send your email straight to spam.
  • Characters: People read emails on all kinds of devices, many of which have small screens. Keep your subject lines under 100 characters, and limit them to 50 characters if you want people to see the entire subject line from any device.
  • Words to avoid: Here are some spam trigger words you should avoid at all costs:
    • Free
    • Income
    • Increase
    • Limited
    • Promise
    • Obligation

Send emails only to people who want them.

If you are buying your email lists and sending them to thousands of customers who don’t know anything about your business, there is a good chance that numerous recipients will flag your emails as junk mail. If enough people do this, your messages will eventually end up in everyone’s spam folders.

Check the technical details.

Make sure the emails are being sent from your business’s domain, with a real reply-to address in your messages, and use a recognizable name in the “from” line.

Improve your engagement rate.

Many of the most popular email providers look at how often recipients open the emails from senders. If your open and read rates are low, your risk of being flagged as spam is higher. By nailing those subject lines and segmenting your list to send only relevant material, you can increase your engagement rate and decrease your “spam score.”

Remove inactive email accounts.

Get rid of so-called zombie accounts, or the email addresses of people who legitimately opted in but subsequently bounced your email or are inactive. Regularly purge your list of accounts that haven’t opened an email within a specific period of time. Every 90 days is the minimum, but once a month is even better. Set up an automated task to remove any email account that hasn’t responded to your emails in the past 90 days.

What are spam traps?

As the name implies, a spam trap is a tool used to catch spammers. Typically, a spam trap is set up by an email service providers and other organizations. They create an email address that looks like it could belong to a real person, but it doesn’t. There is no way for these addresses to be used for communication of any sort, and they can’t consent to an opt-in. Two types of spam traps to be aware of are recycled and pristine.

Pristine spam traps

Pristine spam traps are the accounts made just to identify and catch people using shady tactics to add people to their email lists. If you’re following laws and guidelines, you should never have one of these added to your email list. These traps usually find their way onto email lists that purchase contacts or scrape sites for email addresses.

Recycled spam traps

Recycled spam traps start out as legitimate email addresses. A real person owned these email addresses once upon a time, but they have since been recycled to function as traps for people who fail to follow proper email marketing protocols. Even businesses that are following opt-in guidelines may run into trouble with these if they aren’t cleaning their subscriber lists regularly.

What does all of this mean for you? If you hit a recycled trap once, it probably won’t have a big effect. However, if you hit a pristine trap or get flagged by a recycled trap multiple times, there can be some pretty serious consequences, including the following:

  • Damage to your domain and IP reputation that can be difficult to repair
  • Blacklisting by larger email providers

Getting caught in a trap can devastate your marketing plan and set you back months or even years.

Why emails get blocked

Having your emails blocked is one of the worst things that can happen to your marketing strategy. When this happens, it means your emails are always sent directly to spam or don’t even make it to the spam folder, where they would still have a slim chance of being seen.

Any of the factors that lead your emails to be flagged as spam can also get them blocked. However, there are some other surefire ways to get blocked:

Unauthenticated email address

There is one thing that is almost always sure to get you blocked: an unauthenticated email address. There are a few simple things you can do to avoid this:

  • Send the email from the server and email address you say it’s from.
  • Make sure you have authenticated your email server to send on behalf of your email address.

If you are using a reputable email host and aren’t intentionally trying to mislead anyone, the steps outlined above should be easy. Unless you’ve changed a setting, you probably don’t have to worry about this.

Flagged IP address

If the IP address you’re using to send emails has ever been flagged for sending spam, it can subsequently mark your emails as spam. This is important because, if you send emails through an email marketing service, one of the service’s other customers has the potential to negatively affect your deliverability rates. Use a reputable email service to reduce this possibility.

What are spam laws?

The Controlling the Assault of Non-Solicited Pornography and Marketing Act of 2003 (CAN-SPAM) and the General Data Protection Regulation (GDPR) are two important laws that address spam and data protection. Make sure you understand these laws when developing your email marketing strategy.


This law applies to commercial emails. It grants the recipient the right to opt out or unsubscribe and assigns a penalty to those who violate the act. It’s important to note that this law applies to businesses of all sizes that send emails with the explicit purpose of promoting or advertising a commercial service or product. Additionally, the law does not differentiate between business-to-consumer and business-to-business emails.


The GDPR is considered by many as the most stringent privacy and security law created anywhere in the world. Many people mistakenly think it applies only to businesses operating in the European Union. However, while it is true that the law originated in the EU, it affects anyone who collects data or targets citizens of the EU, regardless of where their business is located.

The process of fully complying with the GDPR is far more extensive than that of CAN-SPAM. Fortunately, once a process has been created and implemented, it can run in the background and blend seamlessly into your lead generation and data security routines.

Image Credit:

Prostock-Studio / Getty Images

Marisa Sanfilippo
Marisa Sanfilippo Contributing Writer
Marisa is an award-winning marketing professional and contributing writer. She has worked with businesses large and small to help them drive revenue through integrated marketing campaigns and enjoys sharing her expertise with our audience.