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Email Marketing

How to Keep Emails from Going to Spam: Key Strategies for an Email Campaign

How to Keep Emails from Going to Spam and Make it to the Inbox

Working in email marketing, we're all bound to face the Gmail spam filter at some point. Even though internet marketing today offers an ever-increasing number of ways for entrepreneurs to reach their target audience, email marketing is still among the most effective e-commerce tools.
The target audience for your product or service may not be active on social media or using messenger apps. But almost everyone has their own email account, hence the impressive reach of this method. However, up to 90% of emails sent every day are marked as spam. Even marketers that provide their subscribers with good content and care about email deliverability sometimes find their emails in the spam folder. Let's discover the underlying cause of this problem.

How Do Spam Email Filters Work

To begin with, it is important to understand the theory. Although we all know what spam is, not everyone understands the concept of spam filters. There are two main methods used in detecting spammers:
  • Automatic – filter parameters are completely under the control of a computer program;
  • Non-automatic – filter parameters are set by a human being and require continual updating (more often than not based on a given list of 'stop-words').
Automatic newsletter list filtering is the most common method as it filters out around 97% of spam based on its self-learning system. These filters work using a number of different techniques, the main ones being:

How Filters Work

1. Checking the Content of an Email Message

The system concludes whether or not emails should be placed in spam based on an analysis of their content. Statistical analysis is used for this purpose. These methods require filters to be trained first. Manually sorted emails are analyzed to determine the statistical features of regular emails as opposed to spam. The method works very well for sorting messages in which advertising information is presented as plain text or HTML. After training filters with a large enough sample, it is possible to eradicate up to 95-97% of spam.

2. Blacklist Checking

There are many IP address blacklists on the Internet, made up of IP addresses that have been identified as distributing spam. The system uses the DNS service to find out whether an IP is blacklisted or not. Therefore, these lists are referred to as DNSBL (DNS Black List). The most common blacklists include the IP addresses of computers from which suspicious newsletters are sent, alongside addresses that have been blacklisted by other systems, dial-up lists, and open relays. The system blocks their domains, and sometimes even their entire networks. In other words, an email is considered spam if it contains links to blacklisted resources, even if it was sent from a legitimate sender.
This method is not all that efficient as spammers are able to find new servers to send emails from just as quickly as they are added to the blacklists. In addition, a few bad apples sending out spam could compromise an entire mail domain or subnet, causing thousands of legitimate users to be blocked from sending emails to the blacklisted servers for an indefinite period of time.

3. Email Newsletter Subject Check

The programs that spammers use to send out spam are also far from perfect. For example, they may not know how to format headers, and the emails may not correspond to industry standards. These characteristics are another indicator used by server programs in order to filter spam emails.

4. Analysis of Email Attachments

More often than not, if spam emails include attachments, these attachments consist of picture files. This method of analyzing newsletter lists for spam allows the system to protect its users from unwanted emails almost every time.

5. Grey Lists

The grey list method is based on the analysis of the behavior of software being used to send spam emails, as normal email server behavior is different from that of spam servers.
This process works in the following way: all previously unknown SMTP servers are considered "grey." Mail from these servers is not accepted but is not definitively rejected either — a temporary error code is returned instead. If the sender-server retries sending after a certain period of time, the server is added to the white list, but if it does not retry, it is added to the blacklist. Regular emails are not lost, but their delivery is delayed. This method currently allows users to prevent up to 90% of spam emails with almost no risk of losing anything important.
You may not be all that enthusiastic about how spam filters work – after all, your carefully prepared newsletters are ending up in spam thanks to filtering. But don't jump to conclusions because these filters also protect users from hundreds of suspicious emails that would otherwise spoil the effect of your newsletters. Every mail system has its own algorithm for working with spam – let's take a look at Gmail's algorithm first of all.

How Does Gmail Determine that an Email is Spam?

There may be several reasons why your newsletter doesn't reach a subscriber's mailbox. Every mail system determines spam in its own way. Gmail has the toughest algorithms of all email clients. Mass newsletters, by default, end up in the Promotions folder, while emails that Gmail deems suspicious end up in the Spam folder or do not reach the user at all.

Possible Reasons Why Your Emails Land the 'Spam' Box in Gmail:

1. You're using an old or purchased database with newsletters sent without user consent

If you have an old database or one which your predecessor bought, it is too bad. After you send out your email, expect one of two things to happen: either users will not respond to the newsletter or they'll mark it as spam. If you are lucky, your addressee will unsubscribe from your newsletter. If you are not, you will have a very difficult time reaching Gmail users in the future.

2. You've seen a sharp growth in your database

If the first email was received by 500 subscribers and the second reaches 5,000, the servers would have determined that you must have received your contacts illegally – hence, your emails would have ended up in spam. While you are 'warming up' a domain, you should increase the number of contacts by no more than 30% per batch over the volume of the previous newsletter.
Advertising can be boring for anyone, sometimes even for those who create it. After receiving another offer to buy something with a discount, install an application, or apply for a credit card, the system will very likely send the next message straight to spam.

3. You're sending overly promotional mailings

Advertising can be boring for anyone, sometimes even for those who create it. After receiving another offer to buy something with a discount, install an application, or apply for a credit card, the system will very likely send the next message straight to spam.

4. You're sending too many emails

Even the most patient of subscribers will complain about spam if they receive ten messages a week from one company. Less is more, both for people and for systems. Only write about things that really matter to users, not just to you. By the way, the algorithms read everything; the content, pictures, text, attachments, and links. Any individual part of an email can affect delivery.
What can one do to avoid such situations? Does anyone really know how to stop emails from going to spam in Gmail? There are definitely several recommendations. We will start with Google's advice and then move forward to our own.

How to Avoid Spam Filters

No one can explain Gmail filters better than Gmail itself. In their blog, the company says the following:
"To keep emails from being marked as spam, follow these guidelines.
  • If the sender's address is in the recipient's contact list, the message is less likely to end up in the spam folder.
  • Sometimes even legitimate messages can be marked as spam. Recipients can uncheck it so that future messages from that sender end up in their inbox."
If we are talking about overall recommendations, some basic pieces of advice are worth considering. We can divide them into two groups – human factors and machine-based errors.
Human factors:
  • Send out your newsletters according to a structured timeline, such as weekly or monthly. This way, there is less chance that readers will classify them as spam.
  • Keep your newsletters thematically oriented, do not turn your newsletters into a purely advertising platform.
  • Be neat and polite, and try to avoid grammatical mistakes.
  • Be sure to leave your address. Readers should be able to write to you if they have a complaint or would like to say thank you.
  • Always leave a visible link to unsubscribe.
Machine-based errors:
  • Use the right words. It is better to write Subscribe / Unsubscribe instead of Remove. For automated systems, this is very important.
  • Pay attention to the subject line of your emails. Some headings scream out 'spam.' Especially those that say "Free," "Respond Now!" or "Money", etc.
  • Try not to send attachments. This will make both filters and your readers unnecessarily suspicious.
  • Use only reputable services and newsletter programs.
Let's take a closer look at these advice and get to the bottom of the issue of how to stop emails from going to spam.
How to Increase Effectiveness of Promo Emails

Best Practice Advice on Avoiding Spam Filters

Email filters can often consider ordinary advertising messages that have nothing bad in them to be spam. To avoid your emails being misrepresented as spam, you need to control the quantity and the quality of the emails you send out. You should continually evaluate how 'spammy' your emails appear.

1. Ask Your Subscribers to Whitelist Your Email Address

By doing this, you will get active consent from your subscribers to read your newsletter – and they'll be expecting it to come. Besides, this action will help avoid spam filters that are searching for newsletters sent without consent or distributed from suspicious email addresses.

2. Check the Email Content & Proofread Your Emails

Remove redundant words from the subject and body of your message. Your subscribers understand that these words are associated with spam. Never use any of the following techniques: aggressive calls to action, promises of enrichment, urgent/short offers, too many exclamation marks, or capital letters in the subject line.
Here are some points that are worth checking before you send a newsletter. Make sure that the email is sent out with links that will lead to pages that actually exist. Do not use shortened links. Avoid using too many photos or too much text. Gmail trims emails larger than 102KB. Don't send a newsletter consisting of one single image.
Also, be sure to proofread your newsletter for errors in grammar, spelling, or punctuation. This task will not help much in avoiding spam filters, but it will greatly increase the respect you get from your subscribers. They will see that you work not only on the content of the newsletter but on its appearance as well.

3. Make Unsubscribing Quick and Easy

Have you ever noticed the "unsubscribe" link in the emails you receive? The thing is, you can't send out a mass newsletter without one. There are two reasons for that:
  1. If a person cannot unsubscribe, they will eventually start marking your emails as spam.
  2. Mail services recognize emails that do not contain an unsubscribe link and may automatically classify them as spam.
There are times when a person no longer wants to receive your emails – do not take it personally. Give them a chance to unsubscribe. Include a clear and a working unsubscribe link at the bottom of the message.

4. Purge Abandoned Email Addresses From Your List

You probably have users in your database who have not opened a single email in the last 3-4 months. It's likely they are not interested in your newsletters or have not checked your products for a long time.
These subscribers are of no use to you — they only reduce your Open Rate, and they themselves no longer need your messages. More importantly, a lot of ESPs charge you for the number of subscribers. So, not only do these subscribers bring you zero money but also they cost you some money when kept in your subscriber base. You can run a reactivation campaign or periodically unsubscribe inactive users: this way, you will increase the engagement of your contact base.

5. Keep to Your Sending Schedule

Spam filters are more favorable to senders who send emails on the same day every week — for example, every Thursday morning.

6. Use a Trustworthy Email Marketing Service

Spam filters take into account a parameter called sender reputation. If you send out emails from a personal mailbox, your reputation will be good by default. Nevertheless, when you need to send hundreds of emails, it's worth turning to mail sending services.
These services have their own reputation in the eyes of email clients. For example, Google knows that good services monitor spammers themselves and are therefore more tolerant to all emails sent through them. It's true: if your database seems suspicious and spammy to the sending service, a specialist will contact you to find out where you got the addresses. After verification, many services aggregate good senders into common server pools whose members have a good chance of ending up in the right folder.
You can also consider not sending emails from your primary domain (like Include a subdomain such as If something goes wrong, this may help save the reputation of your primary domain. It would be a shame if you could no longer send emails on behalf of your website or if your employees' emails stop reaching their clients' addresses.

7. Keep Track of Your Engagement Metrics

Keep an eye on your newsletter statistics. User behavior is the best indicator of newsletter quality. If you see that the open and click-through rates are high, you are doing a good job. If your emails do not get opened, users will start to unsubscribe or complain about spam. If you keep sending emails with bad stats, you risk getting bogged down in spam filters and failing to reach users indefinitely.

8. Keep an Eye on Your Bounce Rate

The Bounce Rate is a measure of undelivered emails. A high Bounce Rate is bad for a sender's reputation. ISPs usually have a Bounce Rate limit, and if a sender exceeds it, they will be warned or blocked.
There are two kinds of Bounce Rate:
  1. Soft Bounce Rate. This is what happens if the recipient's mailbox is full, a message is too big, or there are errors on the recipient's server. If this happens because the recipient's mailbox is full, it might be worth removing them from the sending list — they obviously have not checked their email in a while.
  2. Hard Bounce Rate. This indicates an unresolvable issue on the recipient's end. It occurs if the recipient's email address or domain does not exist or the recipient's server is blocking delivery. Addresses that generated a Hard Bounce are best excluded from the newsletter list as soon as possible. Most ESPs do that automatically, and users don't need to do anything on their own to remove hard bounces from the database.

9. Create a Double Opt-in Subscription Process

A Double Opt-In is a two-step email address confirmation. When a person subscribes to a newsletter list, they receive an email with a special link. By clicking on it, the person confirms that the mailbox works and that they want to receive the newsletters.
Send newsletters only to those who had left their contact details and had explicitly confirmed the desire to receive newsletters. This reduces the number of contacts, but it improves the base's quality in two ways: readers are less likely to unsubscribe and less likely to complain about spam, and this also eliminates the risk of sending emails to non-existent addresses.

10. Configure Email Authentication

There is a way to mark your domain as safe for mail services. To do this, you need to connect a DKIM record, SPF, and DMARC protocol.
DKIM is a digital signature that allows you to vouch for the reputation of a sender. SPF shows which mail servers can send mail on behalf of your domain. DMARC is a protocol that allows you to protect users from phishing using your domain. You can specify these records in the DNS settings. The way these records should look depends on your ESP. Contact tech support to find out what records you should add or change.

How to Test for Spamminess Using Spam Checkers

We understand — it is not easy to keep track of all these parameters on your own, especially if you are only just starting to dive into the topic of email marketing. But don't despair — there are special email evaluation services designed for just this. They help you to check your messages before you send them and prevent them from ending up in a spam folder. Let's take a look at the 3 services that might help you.

1. Litmus

The most popular online service for checking emails and problems that might lead to landing in the Spam folder is Litmus. The service will test your email template on over 90 email clients and devices in seconds and will:
  • highlight any broken links;
  • find images without Alt-text;
  • show how the email is displayed in different browsers and devices (you can choose which clients you want to test your email in).
How the Litmus Test works:
  1. You send a test email.
  2. The service opens the message in various email clients (not emulators, but real devices).
  3. Litmus takes screenshots of what your campaigns look like in different email clients and devices.
  4. You can view the results in your personal account and share a link to the test, if necessary.
There is also an email subject check — the report on it will be included in the "First Impressions" section. If there are any problems with the topic, the system will point them out and suggest fixing them.
Litmus's spam test will help you quickly identify potential problems and give you tips on how to reach a user's inbox. The service will analyze the loading speed of emails, display pictures, and links, and point out the problematic points if it reveals any. In addition to testing, Litmus allows you to create an email in the email editor. There are several ready-made templates for editing.

2. Email on Acid

The Email on Acid web service offers functions similar to Litmus: email testing, an email editor, problem checking, and a spam tester. Testing is offered on 90+ email clients and devices. Screenshots are created from real devices, not emulators. You can check if your message is displayed correctly when Dark Mode is activated.
In Email on Acid, the link test and layout tips are separated into a separate tool which is available in all paid plans. Functionality includes:
  • An email accessibility check: the service will help make the email easier to read for people with visual impairments or dyslexia. Also, based on recommendations on the design of emails, your newsletter will be displayed correctly.
  • A preview header: Campaign Precheck will show the preheader and subject line in several of the most popular email clients.
  • URL check: the service will scan your newsletter list and check if the links are listed correctly.
  • Image validation: you can set a fixed size for images and set Gif-cam to the first frame displayed if the image is static.
Alongside this, the Design Inspiration section has examples of email design. They can help you discover interesting ideas from other companies and brands.

3. Mail-Tester

Mail-Tester will not display emails on different devices but will highlight errors that could cause the campaign to end up in spam. This online service evaluates the newsletter on a special spam rating scale. It is primarily set up to check newsletters (to pass the Apache SpamAssassin filter), but in principle, works well with any type of email. On this platform, you do not need to sign in or register to do a test campaign.
A random email address is generated each time you can send a test email. When you click the "Check Score" button, the email goes to check. As soon as the boat stops — your email is detected, and you will see the results on the spam rating and recommendations in order to improve the email.
The maximum result in the Mail-Tester is 10/10, and you will be given tips on what you need to fix in the campaign to improve its performance. For example:
  • put in Alt-text;
  • add more text;
  • adjust SPF and DKIM.

To Sum Up

Competent email marketing helps you build and strengthen quality relationships with your target audience. It is necessary to do everything possible to ensure your efforts to create high-quality content and collect a base of loyal subscribers do not go down the drain.
Now you know how to stop emails from going to spam and how to make sure that your newsletter is useful and attractive. You might even have some serious work to do. Of course, you won't necessarily end up in spam because of one slip-up, but if you don't follow at least half of our recommendations, you're in a high-risk group.
Try to follow all the advice you found in this article. However, if you are still not sure about the quality of your newsletters, use one of the spam checking services we wrote about above. Good luck!
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