Spam Filters

What is Spam Filter? How Spam Filters work? How to avoid getting caught by Spam Filters?

Jelena avatar
Written by Jelena
Updated over a week ago

Spam filters use a lot of different criteria and algorithms to assess incoming emails, identify spam, and block it or place it in the spam folder. After evaluating each factor, spam filters assign a numerical score to the probability of the message being spam.

This score determines if an email will pass through the filter. Passing scores can vary depending on the server, so an email could pass through some filters but not the others.

The best way to avoid this is to better understand how spam filters work.

What Spam Filters Look For

Not all spam filters function the same way, but there are some basic characteristics of spam. Here are some common things spam filters look for, and how to avoid them.

  • Content filters – review the content within a message to determine if it is spam or not.

  • Header filters – examine the email header source to look for suspicious information.

  • General blacklist filters – stop all emails that come from a blacklisted file of known spammers.

  • Rules-based filters – leverage user-defined criteria – such as specific senders or specific wording in the subject line or body – to block spam.

  • Permission filters – require anyone sending a message to be pre-approved by the recipient.

  • Challenge-response filters – require anyone sending a message to enter a Captcha in order to gain permission to send an email.

The Source of the Email and the Reputation of the Sender

Anonymous and free email domains, such as Gmail, Yahoo, etc. are often filtered more aggressively than verified email domains. Since we are using your own SMTP for sending emails, we recommend that you set up your email address using a private domain name. However, even private domains need time to develop a good sending reputation. Sending a big email campaign from a brand new domain before your reputation is established can lead to bad consequences. So, if you have a brand new account, we strongly suggest that you start by sending 10 emails per day. 

Of course, before you go on and use any kind of email automation, it is preferable to warm up your email account manually. This means approximately a week of manual usage and making sure you send tens of emails to known recipients from the browser itself.

Also, some spam filters will flag your emails if anyone with the same IP address has sent spam. 

You should consider setting up your email authentication also. Having SPF, DKIM and DMARC properly set up can help increase email deliverability. 

Content and Format

Email subject line and email content should be valuable, interesting and personalized as much as possible.

Here are a few things to keep in mind about content and format.

  • Skip the wild formatting like neon colors, using ALL CAPS or a dozen exclamation points, emoticons, and similar. 

  • Include our Unsubscribe link and give your contacts an easy way to unsubscribe.

  • Too many or too big images can raise a red flag. The same goes if you try to send an email that contains only images. 

  • Test all links before you send your email and avoid link shorteners.

  • HTML codes can trigger spam filters (that is why HTML templates are not allowed inside Autoklose.) 

Spam is a real issue and should be taken seriously, especially if we have in mind that it can lead to bad and permanent consequences. Following these few simple rules will help you avoid getting your emails flagged as spam and will also improve your deliverability.

— — —

If you have any questions do not hesitate to initiate a live chat.

Your team!

— — —

To learn about sales, customer acquisition, business strategy, and more, read our 50,000 subscribers strong blog.

Join over 10,000 followers on LinkedIn, to learn just released success stories from around the world of business.

Did this answer your question?