Your domain or IP has been blacklisted

Step number 1 is to check if your email server has actually been blacklisted. Even though this is most often not the case. It rarely happens to established companies that use the well-know email marketing systems like Apsis, MailChimp, Active Camping or others, but it is a good idea to check just to be sure. Check whether your domain, IP address or mail server is blacklisted on this website or on the DBL Blacklist.

I could also be that the so--called SPF records (Sender Policy Framework), which is an "email authentication" are not set up correctly. This means that your domain is not "allowed" to send from the server and can therefore be marked as spam.

If you are looking for something more specific about SPF setup of Exchange or Mailjet you can find it in these articles:

Your recipients have stopped opening and clicking on links inside your emails

Gmail, Outlook and other major mail providers use a technology to assess the relevance of the mails that are sent. And they assess the relevance based on whether the recipients open, click on links and generally interacts with emails from the recipient in question.

So when your recipients interact less with your emails they more often end up in spam where the likelihood the them being read decreases significantly.

You can therefore easily find that your email ends up in the spam folder of one Outlook user and in the inbox of another.

The interaction of the recipients of your emails is one of the most important parameters for whether your emails end up in the spam folder or the inbox.

You use typical spam words ands characters in your subject line or subheader

The REAL spam mails often contain a number of the same words, characters and expressions that many spam filters look for.

It could be, for example, "money", "free", "cash", "win", "your winnings are waiting", "luxury" etc. or $ signs, £ signs or the like.

You use CAPITAL LETTERS and too many exclamation marks!!!

In general, capital letters and exclamation marks must be used with care in written communication because they have the potential to annoy the recipient of your mail. (Hint: The same applies if you indicate your email as "Important" with the red exclamation mark in e.g. Outlook.)

But for the spam filters capital letters, too many exclamation marks and question marks can be an indication that your mail is spam. So minimize or avoid them altogether.

There is too much emphasis on images and links, or not enough text

Too many and too large images in relation to the amount of text can weigh negatively in your spam score.

You are of course allowed to include pictures, but think about the amount and remember to put the same links in text as behind the pictures, so that the spam filter can see that there is meaning behind the "madness". Likewise, too many links can be a sign of spam so do it in moderation.

You are missing the basic information and the option to unsubscribe

It MUST be possible to unsubscribe from your email. Usually this is an integral part of email marketing systems and probably not a problem for you. In addition, contact information, a link to your personal data or to you "Preference Center" can be a good thing to include, because it also increases transparency and the goodwill of the recipient.

You use colored and/or formatted text

Many spam emails use colors, repetitions, blank lines, formatted text or spaces such as C O N G R A T U L A T I O N.

Or they replace letters with numbers such as g00gle.

Spam filters are extra sensitive to this.

In terms of colors, red, green, blue text in particular should reportedly be something that spam filters detect because it is often used for offers or warnings.

Hidden code: You have copy-pasted tables or text with HTML code into your email

The credibility of your email drops drastically if there are errors in the HTML code in the template, text or tables.

This can happen, for example, if you copy content from a Word document into your email.

In addition, there is a limit on how much HTML code can be included in your email. If the code takes up more than 100KB Outlook and Gmail can cut off the bottom part of your email and insert a link to the rest of the content instead.

You suddenly increase the amount of emails to your recipients

Spam often comes in large quantities and therefore many email providers such as Gmail or Outlook react if a lot of emails suddenly are sent from an account that does not normally send many emails.

This can happen, for example, if you have created a new email list, newsletter or something else and are waiting for the list to become sufficiently large before you send out emails. A good piece of advice is that you always send out a welcome email when people sign up and then continuously send emails to the list of recipients, so that the email flow does not suddenly change frequency.

Spam test your email

Many email providers do this automatically so normally this would not be an issue.

But if you want to be sure you can run a spam test yourself. You can do this here.