How to Avoid Spam Filters?

Every e-mail marketing professional starting a campaign expects high open, replies, and conversion rates. However, quite often, the spam rate takes over. It happens for two reasons – ESPs spam filter problems and the way the recipients interact with your e-mails. Unlike filters, based on auto analysis and algorithm, the human factor is more unpredictable. If the content doesn’t correspond to the recipients’ desires, needs or the message looks odd, they might mark it as a spam.

In this article we’ll cover everything you need to know about how to avoid spam filters and prevent your e-mails from being marked as spam.

What Exactly is Spam?

Spam (also known as junk e-mail) is unsolicited e-mails sent in bulk to people who didn’t give their consent to receiving them to promote, spread malware, or phish.

The critical characteristics of spam e-mails are:

  • Unsolicited
  • Invisible headers
  • Poor spelling and grammar
  • Asking for suspicious actions or information
  • Bulk sending (more than 10 recipients)
  • Anonymous senders
  • Spammy subject line
  • Bright e-mail body with lots of pictures, colors, and fonts
  • Multiple links
  • Irrelevant or suspicious attachments

All of these points can affect your e-mail deliverability. However, there’s more to how e-mails end up in the spam folder than poor grammar and attachments. Let’s take a closer look.

How to avoid Spam filters when sending emails

Your e-mails can land in the Spam folder in two ways – by getting flagged by the e-mail service providers’ (ESPs) spam filters or by having the recipient label your e-mail as spam manually. This is how to avoid spam filters. We will get into specifics in more detail below.

E-mail service providers analyze everything – how many of your e-mails you have sent before, how many e-mails you are trying to post right now, where you are sending them from, and how many of your e-mails get opened, which takes us to the human side of this problem.

How the recipients interact with your e-mails affects your sender reputation, which will then determine if you’ll be able to send e-mails again. Everything from e-mail opens to spam complaints (obviously) affects it.

By avoiding suspicious behavior and fine-tuning your e-mail copy, you’ll maximize your deliverability and keep your reputation pristine.

How to avoid spam filter algos?

As the first step of e-mail analysis is conducted automatically by an algorithm, you should be aware of the technical sides and its influence on your e-mail deliverability.

1. Avoid using any dynamic IPs

dynamic IP is used by two or more people simultaneously, for instance, when using the same local Wi-Fi connection (at work, home, or in a cafe). If you use an IP that was previously used for purposes you can not control, you won’t be able to control its sender reputation. As you know, with a low sender reputation comes higher chances of getting flagged as a spammer.

Therefore you need a dedicated IP address to be on the safer side. A dedicated IP is a unique address associated with a definite hosting account that only you can access.

2. Check the IP reputation on a regular basis

If you’re unsure about the reputation of your IP, you can always check it. Numerous free apps can help you do that. We recommend Talos Intelligence, Reputation Authority, or Sender Score for detailed reports.

3. Verify all e-mail lists

First of all, we don’t recommend purchasing e-mail lists. That said, any e-mail list you have, you have to verify beforehand, including those you have checked before. Regardless of the source, you cannot be one hundred percent sure of the list’s quality, because e-mails get abandoned, mistyped, or blocked every day. As time passes, any e-mail list will need a cleaning. So, why are verifying e-mails so important?

When you send e-mails to invalid e-mail addresses, they bounce. The higher the bounce rates, the lower your reputation, and the lower your IP reputation, the closer you are to being blocked by the ESP. So, you always need to be sure that the e-mails you send will reach actual recipients. Plus, it’ll save you a huge chunk of your budget. Always verify and test e-mails. You can choose an e-mail tester based on your needs and business type.

4. Follow your e-mail campaign open and spam complaint rate

Having low open and high spam rates is the shortest way to being suspended by the ESP. Follow how your campaign is actually performing, and edit accordingly to improve your results.

High unsubscribe, and spam complaint rates are mostly caused by incorrectly chosen e-mail frequency or the low quality of your e-mail content.

If you need to compare your rates, below is the industry average:

  • The average open rate is 15.1 percent for B2B and 20.81 percent for B2C
  • The average unsubscribe rate is 0.23 percent
  • The spam complaint rate threshold is usually 0.5 percent

5. Know your bounce rate

The bounce rate is the ratio of e-mails that haven’t reached the recipients’ inboxes to the general number of sent e-mails. There’s a big difference between hard and soft bounces, but the higher the bounce rate, the more significant the damage to your sender reputation. The ideal bounce rate is Zero, but it’s not very realistic. You should try to keep it under 2%.

6. Warm-up new e-mail accounts before sending large campaigns

If you send massive e-mail campaigns to over 500 recipients, read on. If you deal with vast amounts of e-mails on regular basis and change your sender accounts every now and then, you need to first remember to warm them up. Start with one e-mail a day (that is sure to be opened) and keep increasing this number day-to-day to improve your sender reputation.

7. Create a separate e-mail account for outbound marketing

When sending outbound e-mail campaigns, you need to be 100% sure of your status. Unfortunately, it may be a tough task when the whole company is using the same domain name and IP address.

This is why several companies create a separate account and domain account for their outbound campaigns – to be able to control the sender’s reputation and have confidence that they are the only ones responsible. It’s an excellent idea to keep all your e-mail campaigns separated – outbound, marketing, newsletters, transactional e-mails, etc.

8. Set up DKIM, SPF, and DMARC records

DKIM, SPF, and DMARC are the three protection steps that can save senders from hackers, phishers, and data capture, and avoid the recipients’ spam folder.

Sender Policy Framework (SPF) is a unique DNS record that contains all the IP addresses from which you can send e-mails from your domain name. The SPF checking is the first step in e-mail authentication. If the recipients’ server locates your sender IP in the SPF record, it will let the e-mail pass through to the second check process.

Domain Keys Identified Mail (DKIM) on the other hand is the mechanism that works using two unique encryption keys, private and public. This is the second step to prevent spoofing. The private key encrypts the invisible header in every e-mail. The public key is the TXT record in the DNS record. When the recipient’s server gets an e-mail, it requests the public key and decrypts the header to prove that you are the sender. If you don’t set up the DKIM, mail servers will simply decline your e-mail.

Domain-based Message Authentication Reporting & Conformance (DMARC) is a protocol that defines what to do if the sent e-mail hasn’t passed the first two authentication steps (DKIM and SPF). This is the third and final step in e-mail authentication. You can set one of the 3options: take no action on the e-mail, mark the message as spam, or reject the message.

9. Avoid spam trigger words

Every sent e-mail is analyzed in detail. Every word, as well. If you overuse words that trigger filters, like free, 50% discount, buy now, etc., your e-mail may be sent to the Spam folder. You can read a list of 550+ spam words on the internet to keep your e-mail copy clean. Or you can use online tools like Email Copy Checker to test your e-mails in case you forget to check your message for spam words.

10. Be careful with HTML

Poorly coded HTML is a pretty distinctive feature of spammer e-mails, and the filters know it. Ensure your HTML template is perfect, or don’t use HTML at all.

11. Stick to the optimal text to picture ratio

Pictures are loved by spammers because they’re a great way to hide spam trigger words from the spam filters. That’s why overusing pictures can actually catch the attention of spam filters. The best text to picture ratio is 80 to 20.

12. Send personalized e-mails

Spam is essentially bulk e-mails, sent with no regard to personal approach. This means that spammers don’t often bother with targetting, and every e-mail looks just the same. The spam filters are looking out for it. To avoid your e-mails looking like spam, you need to add a little personalization to each of your e-mails. This can be the person’s first name, last name, company, etc., there is no limit to it.

Not only will adding more personalization help you avoid spam filters, but it will also improve your open rates, click-through rate, and sometimes even conversions. Use custom e-mail variables to add a human touch that will look real to both the ESPs’ filters and the recipients.

13. Go easy on attachments

E-mail deliverability is majorly affected by the e-mail size. Experiments show that the larger the e-mail, the more often it is filtered as Spam by ESPs. Hence, the open and conversion rates fall, and the spam rate increases. The solution is very easy: instead of sending the file as an attachment with the e-mail, include links to Google Drive (which, by the way, are automatically scanned for any viruses and look trustworthy to both the ESPs as well as recipients).

14. Comply with e-mail laws and regulations

Under the CAN-SPAM Act, the sender should follow specific rules to be on the safe side. They are:

  • Don’t send e-mails through open relay
  • Include one unsubscribe option at the end of the mail
  • An e-mail should contain the true header
  • An e-mail should contain at least one sentence and not be null

The CAN-SPAM Act is one of the significant regulations. Make sure your campaigns comply with the rules of your (and your recipient’s) countries.

15. Track links right

Link tracking is essential when it comes to analyzing your e-mail campaign’s success. That said, it can hurt e-mail deliverability if done the wrong way. The best way to include any links in your e-mail copy is by using anchor words instead of adding the link as is.

How to reduce spam report rate

If the e-mail content doesn’t suit the recipients’ expectations or they simply don’t want to receive e-mails from you, they can either unsubscribe or worse – if they suspect your e-mail is spam they will send it to Spam folder or report as abuse to a blocklist center. So, how do you reduce spam report rate? Simple. By following a couple of rules (and of course some common sense).

1. Receive people’s consent to e-mails

While cold e-mail is a real and valid e-mail marketing option, you’ll still get better results with inbound e-mails to people who have actively chosen to receive e-mails from you. When you receive people’s consent to receive e-mails, you minimize the chances of them reporting your e-mails as spam. Set up a form on your website and inform buyers that you would like to send them e-mails to receive consent.

2. Learn how often people want to receive e-mails from you

If you receive e-mails from a particular sender too often, even if you have subscribed to them, you can get annoyed by marking them as spam. Therefore you should learn the e-mail frequency best practices for B2B and B2C to avoid ruining your reputation and maximize your e-mail marketing results.

3. Never use misleading subject lines and headers

Never give false promises if you are not going to go through with them. Giving your e-mails deceptive subject lines and headers will destroy the trust the recipients have in you when they open your e-mails and will increase your spam report rate. Learn how to write a great e-mail subject line to improve your open rates, and never try to deceive your readers.

4. Use a trustworthy and clear sender name

The recipients are unlikely to trust if they don’t know who you are. To avoid this, you can:

  • prevent obscure e-mails like
  • don’t change your sender name very often
  • make it recognizable for them by including your full name or the company’s name you work for (e.g., Maryna from Deliverbility.comEileen at ABC)

5. Avoid multiple fonts, colors, and capitalized text

Besides, being negatively perceived by most spam filters, an overabundance of fonts, colors, and capitalized texts can also awake distrust in the recipient. If the opened e-mail contains hard to read the text in multiple colors, with every sentence written in a separate font, and the subject line or big chunks of text in caps, it will scream SPAM to anyone who has been online long enough to know what a spam e-mail looks like.

Nevertheless, if you’d still like to play with your colors and fonts a little without harming your sender reputation, we’ve created separate guides on how to use fonts in an e-mail and using colors in e-mail marketing. Check those out. The gist is – never use more than 2 easy-to-read colors (one for the main text of the mail or background and one for the CTAs), use a single font, and once and for all totally forget about CAPS – there’s absolutely no need to yell at your recipient. Right? Ideally, use only your standard corporate colors and fonts to make your e-mails visually recognizable, unique, and trustworthy.

6. Let the recipient know you’re sending a promotional e-mail

According to the CAN-SPAM Act, if an e-mail is promotional or an advertisement, it should be disclosed in the e-mail body. You can add this info at the end of the e-mail. For instance, This advertisement was sent by ABC Company.

7. Double-check your grammar and spelling

Avoiding grammar and spelling mistakes as an e-mail marketer is less advice and more common sense. Still, it’s especially relevant in the context of spam complaints. Poor spelling and grammar are a distinct feature of spam messages. The exact reasons behind this are unclear though – maybe misspelling words helps to avoid certain spam filters, or perhaps phishers simply don’t pay much attention to the quality of their lives.

One thing is clear, however, mistakes don’t look good in the eyes of your e-mail recipients, and an overwhelmingly huge number of mistakes can cause disappointment and anger to such an extent they start sending your e-mail to spam.

8. Insert just one link with a very clear and straightforward CTA

If you want your CTAs to really work, your link has to look legitimate. Therefore, make sure it describes in very clear terms where it’s going to take the recipient – a suspicious link is one of the primary reasons e-mails get labeled as spam. Besides, you should use just one link with the CTA. This is because using multiple CTAs can distract the recipient from the primary goal of your email campaign.

9. Ask for simple and innocuous actions

What do you really do if the sender asks you to send some money? Or open an attachment you aren’t even expecting in the first place? Or follow a shady link to an unknown website you don’t remember signing up for? I don’t know about you but I always mark such messages straight to my spam folder. And who wouldn’t? You should learn from others’ mistakes and do not ask people to perform questionable actions they wouldn’t be comfortable with.

10. Allow your recipients to unsubscribe from your mailing list

Everyone should have the right to unsubscribe from receiving your emails if the content of the e-mails they receive doesn’t correspond to their needs, preferences, interests, or wishes. Therefore you should always give the recipient a way to opt-out, whether through a reply option (best for an outbound campaign) or an unsubscribe link (inbound campaign).

11. Do not send e-mails to generic corporate e-mail addresses

Sending to generic e-mail addresses like,, etc. is unlikely to result in a higher response rate. Such names give little room for personalization. None of this is right for your sender reputation. This is why we recommend to send e-mails to personal, corporate e-mail addresses and personalize your e-mail copy as much as you can.

Always be on the safer side

All the mentioned tips are crucial while sending an e-mail campaign. However, sometimes things go awry even in the best-planned campaigns, which is why you should always send a test e-mail.

You can find lots of tools online that check if the e-mail you’re going to send will pass through all the spam filters or not. Nonetheless, replicating the real conditions is the only sure way to find out if your e-mail will reach the inbox. Send a spam test e-mail to make sure you didn’t forget any of the points.