How to prevent Email being considered spam

The success of Email Marketing campaigns depends on the Delivery Rate. Similarly, the sender's reputation, the contact list, the frequency of sending and the content of the Email are all factors that affect it.

It doesn't matter how well you create Email content, if it never reaches the inbox, it's considered spam, and visitors are significantly less likely to open it and click on the CTA buttons.

How to improve the delivery rate

The more your audience interacts through opens and clicks and the less they complain that it's "spam", the better your Delivery Rate will be.

To be recognised as a legitimate sender and prevent your Email from being sent to spam, we suggest some recommendations to follow in your email marketing campaigns:

• Check that your domain has been validated on the Closum platform. You can find out more about this in our "validate-domains-for-sending-newsletters" document in our Knowledge Base;
• Keep the subject line between 35 and 50 characters. The longer the subject line, the more likely it is to be flagged as spam by Internet Service Providers. In addition, building strong and impactful subject lines will attract readers' attention and generate better Open Rates.
• Don't use all capitalised words in the subject line or body, as this can be dubious for ISPs;
• Try to minimise the use of bold, red letters, exclamation marks and symbols such as "€ $ @ and £" in Email copy;
• Avoid using certain words frequently identified by spam filters so as not to be mistaken for a spammer (or worse, a phisher);
• Avoid sending messages consisting of a single image or several images. Make sure you have a balance of approximately 70 per cent text and 30 per cent images;
• Make sure you send content that is relevant to your subscribers. If you send non-relevant content to your contact list, subscribers may unsubscribe or mark you as a spammer. With relevant content, you're more likely to increase your open and click-through rates and thus get a better reputation.

Results

Optimising the content of your Email Marketing campaigns is one of the main keys to maximising deliverability.

If you have any questions, you can contact our team by email: [email protected] or via the live chat available on Closum.

Updated on: 08/07/2025