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If you’re like most marketers, your email efforts most likely build on the essentials: growing a quality list, designing great emails, and writing amazing copy. With a quality email, you’ll surely avoid spam filters, right?

Not necessarily.

Many factors play into email deliverability. These factors ultimately determine whether or not your emails are delivered successfully.

The thing is, you should be ever-vigilant when sending emails to your contacts. Avoiding spam filters is an important part of maximizing the opens, clicks, and sales you get from your email campaigns.

So how do you do avoid spam filters? How do you ensure your campaigns are delivered to your subscribers’ inboxes and not filtered out?

In this guide, we’ll teach you about the factors that determine whether your email campaigns find subscriber inboxes or not, and what you can do to increase your chances for quality email deliverability.

Chapter 1

The importance of spam filters

According to estimates, there are over 180 billion spam messages sent every day. Worst of all, spam can work.

In fact, companies lost $676 million to spam emails from fake vendors in 2017.

In order to protect their users, inbox providers like Gmail, Outlook and Yahoo Mail use spam filters to help ensure these messages don’t clutter up their user’s inboxes or worse, harm their users.

These spam filters act like a shield, analyzing incoming emails and allowing the good ones to reach the inbox while filtering the bad ones into the spam folder (or rejecting them completely).

While this might seem a bit technical, it matters to marketers. Spam filters are similar to a sales funnel:

There are a number of steps your email campaign goes through in order to drive results for your business.

Before you generate a single website visitor or sale from your campaign, your email must first be delivered to your subscriber’s inbox, opened, and finally clicked.

However, if your campaigns aren’t making it past the spam filter, then they’ll never be delivered to the inbox, and won’t have the chance to be opened, clicked or drive results for your business.

Chapter 2

Spam filters explained

In the past, spam filters would analyze the content of your campaigns looking for signals that determined whether they should send your emails to the inbox or not.

Phrases like ‘Lose weight fast’ and ‘double your income’ were all obvious signals that would increase your spam score and cause your campaigns to get caught in the spam folder.

These days however, email providers like Gmail, Yahoo and Outlook have gotten a lot more advanced with their methods.

Now, whenever you send a new campaign, inbox providers like Gmail and Outlook actually look at their user engagement and previous interactions with your past campaigns. They then use this information to determine whether your latest campaign makes it to the inbox or not.

Specifically, they look at the following factors:

Good Signals

  • Open – If a user frequently opens your campaigns, this is seen as a good signal that your campaigns aren’t spam and helps your emails make the inbox.
  • Reply – If people respond to your email campaigns (via reply email), this is seen as a good signal and helps improve your reputation with email providers.
  • Not junk – If people move your email out of the junk folder, this is considered a very strong, positive signal that your campaigns are relevant and worthy of making the inbox.
  • Move to folder – If your recipients move your emails into various folders in their inbox, the email providers take this as a sign they care about your emails and are more likely to continue delivering them to their inbox.
  • Add to address book – If your recipients add your email address to their address book, the email providers take this as a sign that they care about receiving email from you and are more likely to continue delivering them to the inbox.

Bad Signals

  • Move to junk – If people move your email to the Junk folder, this is considered a very strong, negative signal that your email campaigns aren’t worthy of the inbox.
  • Delete without open – If your recipients take a quick glance at the sender and subject and then delete your campaign, this is seen as a negative signal.


These factors all combine to give you 2 unique scores:

  1. Your score with the individual subscriber – If an individual subscriber is always opening your campaigns and moving them to folders, then you are going to build up with that individual subscriber.
  2. Your score with the email provider as a whole – If majority of your Gmail subscribers (for instance) are opening your campaigns and moving them to folders, then you are also going to build up a great reputation with Gmail as well.

And when it comes to deciding whether to deliver your latest campaign to the inbox or not, email providers like Gmail take both of these reputations into account.

So for instance, you could have a great reputation with an individual subscriber who always opens your campaigns. However, if your reputation with the inbox provider (e.g. Gmail) is poor because they see that the majority of their users are junking your campaigns, then nobody will receive your campaigns (even the individuals who were engaged in the past).

Chapter 3

How to avoid spam filters

As you can see above, whether your campaigns make your subscriber’s inbox or not largely comes down to people’s previous engagement with your campaigns.

If they’ve opened and clicked on your previous emails, then your next campaign is likely to make the inbox. If on the other hand, they’ve deleted them without opening them, it’s more likely your latest campaigns could end up in the spam folder.

So how can you make sure people are interacting with your emails and sending positive signals to inbox providers?

Our deliverability team works with our customers all day long to help them achieve that goal, so we asked them to share the top 5 things marketers like you can to do to help get your emails delivered:

1. Only email people who have given you permission

Rather than wasting your money buying or renting email lists, focus your efforts on building your own email list.

Lists that are built organically (through people opting-in to receive your emails) have open rates 5x higher than purchased or scraped lists, and receive 4x fewer spam complaints.

These increased opens and reduced spam complaints are positive signals in the eyes of email providers, and help ensure your campaigns get delivered to your subscribers inboxes.

So how can you build a high-quality, permission-based email list?

In our list building guide, we outlined a 2-part formula you can use to build your email list:

Valuable incentive + simple subscribe opportunities = A huge email list

By offering an amazing incentive (such as great content, exclusive discounts, etc) and having prominent subscribe opportunities that make it easy to join your list, you can build a high-quality email list that ensures your email campaigns get delivered to everyone.

2. Use a familiar ‘From’ name

According to research, 68% of Americans base their decision to open an email campaign on the From line.

Given that opening a campaign sends strong positive signals to email providers, the From name is a critical element of your email campaigns to be optimizing.

So how do you do it?

The key to success is to use a ‘From’ name your subscribers will recognise.

For instance, imagine you subscribed to an email newsletter from the BuzzFeed website. Would you expect to receive emails from ‘BuzzFeed’ or from ‘Dan Oshinsky’?

Given that you’ve signed up for these emails from the BuzzFeed website, chances are it’s the earlier, even though it’s actually Dan who is creating and sending their campaigns.

3. Use segmentation to send targeted, relevant campaigns

Rather than sending the same email to your entire list, try segmenting your list and targeting the campaign to those who you know are going to be interested.

By doing so, you’ll increase the number of recipients opening your campaigns and decrease the number of people deleting them, sending positive signals to email providers about the validity of your campaigns.

Notice how Society6 uses segmentation to send Galentine’s Day emails to their female customers.

Although Society6 sells items for all genders, they know who their female subscribers are and use that information to make a niche campaign.

This increases the number of recipients opening and engaging with their campaigns, and sends positive signals to email providers that their recipients want to be receiving their emails.

4. Use a real reply-to address in your campaigns

As mentioned earlier, one of the key signals email providers like Gmail and Outlook use to determine whether your latest campaign makes the inbox is whether or not you have received responses to your previous emails.

This makes sense. Nobody ever responds to spammers or to email they don’t care about, they simply ignore or delete it. So if you’re getting responses to your campaigns then it’s an obvious signal for email providers that these are legitimate emails people care about.

So when creating email campaigns, try to avoid using emails like as the reply-to address.

Email addresses like this tell people you are not interested in hearing from them, and reduce the amount of responses you get.

Instead, try using alternatives like:


Seeing these kind of emails addresses encourages people to respond, and those responses are interpreted as positive signals by email providers that help improve your ability to land in the inbox.

5. Configure your account to send from your business domain

When you sign up to use email marketing software like Campaign Monitor, not only do you get tools to create beautiful, on-brand email campaigns, but you also get access to our sending infrastructure to deliver your campaigns to your subscribers.

By default, your campaigns will be sent from one of the generic domains we maintain (such as or However, there is a setting in your account you can enable that will allow you to send your campaigns from your own domain name (i.e.

When you do this, you send strong signals to email providers like Gmail and Outlook that you are a legitimate business sending legitimate email campaigns, as spammers generally don’t take the time and effort to go through this process.

So in order to help get your emails delivered, you should spend some time setting up your business domain in your email marketing tool (Campaign Monitor customers can do so by following the instructions here). It’s quick and easy to do, and will help ensure your email campaigns make it into your recipients inbox and drive sales and revenue for your business.

Chapter 3

Wrap up

Avoiding spam filters and getting your campaigns into the inbox isn’t usually top of mind for most marketers, yet it can have a huge effect on the results you get from your campaigns and can give your brand an advantage over your competitors.

So as you go about executing your email marketing initiatives, think back to some of the tips presented in this guide. Send to permission-based email lists, configure your account to send from your business and send relevant, engaging campaigns.

Doing so will not only increase your open and click-through rates for that email, but will send positive signals to email providers that will help ensure all future campaigns you send to your subscribers land in the inbox.

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