How can I prevent my emails from ending up in SPAM?

This article discusses why your emails may end up in the spam folder for contacts, and what you can do to improve the deliverability of your emails.

Topics covered in this article

Domain Authentication (DNS)

First and foremost, it is essential to carefully check your DNS records, as they contribute to the deliverability of your emails.

Keep in mind that your main focus should be on maintaining a healthy contact list. Focus on sending relevant content to interested contacts and encourage interaction. Good delivery of your emails will follow if you maintain this focus.

For instructions on linking your domain to MailBlue and setting up your DNS records for domain authentication, you can refer to the following help article: How do I connect my sending domain to MailBlue? (DNS)


General Advice

Despite having completely correct settings, it is never entirely possible to prevent emails from being received in the spam inbox. Each receiving email provider has its own filters to determine if emails are spam. To minimise the chances of your emails ending up in the spam inbox, here are some effective tips:

  1. Delete inactive contacts

    If you regularly send emails to contacts who do not open them, the spam filters of receiving providers will filter your message as 'unwanted', causing your email to be sent to the spam folder. It is therefore advisable to regularly delete inactive contacts and keep your lists clean. You can do this by using the engagement tagging automations available in our software. As a general rule, you should only email contacts who have opened an email from you in the past 12 to 24 months to maintain excellent deliverability. It also helps to prevent natural list shrinkage by regularly finding new ways to attract subscriptions. The older your list and its associated data are, the more difficult it becomes to guarantee your deliverability.

  2. Focus on valuable content
    If the content of your messages is valuable to your contacts, they will continue to open your emails and your emails will be correctly delivered to their inboxes. Make sure to send content that your subscribers have consciously subscribed to and regularly send new, interesting, and related content. If you only send promotional or sales emails, you will notice a significant decrease in open rates and deliverability.

  3. Review your registration process
    Try to put yourself in the shoes of your (potential) contacts. What do they expect to receive from you after registering? If you send emails that they did not expect, there is a high chance they will not read them or mark them as spam. Think about the 'tone of voice' you use and make sure it is clear what someone is signing up for. Additionally, keeping the design of emails consistent also helps. If you frequently change the design of emails and/or the logo, this can cause confusion among your contacts, leading them to mark the messages as spam.

  4. Send targeted and personalized emails
    When sending an email to a large number of contacts, the likelihood of receiving a high number of spam complaints is obviously greater than when sending to a smaller number of contacts. To prevent spam complaints, it is valuable to segment this large number of contacts based on behavior or interests. This way, you can send targeted and personalized emails, reducing the chances of complaints. A thank you email or welcome message can of course be sent in bulk. Contacts will receive these based on an action they have taken, making them expect the email. With an expected email, the likelihood of spam complaints is minimal.

  5. Ensure a pleasant sending frequency
    If you have a larger list, it is important to find the right sending frequency. If you send too often, contacts will quickly find your messages annoying, but if you send too infrequently, you are not working on optimizing your sending reputation. The right frequency largely depends on the relationship you have with your contacts. Generally, twice a week is considered non-annoying, while also working on your sending reputation.

  6. Use the MailBlue spam check
    In the summary of each campaign or automation email, you can see if your message passes the spam check. If there are any noticeable issues, this tool will indicate them. You can use this article to address any notifications.

  7. Always send emails with text
    The definition of email is that it is digital mail used to convey information. To ensure good deliverability of this digital mail, it is important to include text in the email. An email composed solely of images may potentially cause delivery issues. The use of images does not necessarily impact email deliverability, as long as they are combined with textual elements and there is a good balance between text and images.

  8. Use a business email address 
    Use a business email address linked to your website domain, instead of a free email address like or This enhances sender reputation and deliverability.

  9. Pay attention to the links in your emails
    Receiving providers' spam filters check all links you refer to in an email. If you refer to a domain with a poor reputation, there's a high chance that receiving providers will flag it and consequently land the email in spam.

  10. Avoid using URL shortening services (like
    Links to web pages can sometimes be very long. Despite this potentially being undesirable in an email, it's still recommended to use them without modifications. Shortening links - as possible with for example - is highly susceptible to spam. To avoid visually displaying the longer link, you could place it behind a button, piece of text, or image as an action in the email.

  11. Send consistently from one sender name and email address
    Sending consistently from one sender name and email address helps you build a sending reputation with this information, which improves the deliverability of your emails. If you frequently change these details, it will have a negative impact on your sending reputation. Therefore, make sure to carefully consider the desired sender name and corresponding email address. It is important that these are recognizable to your recipients.

  12. Regularly check your automations
    If you have automations active in your MailBlue account, check them regularly. This way, you can quickly identify any issues affecting the deliverability of your emails. For example, if you notice that specific emails are not being opened, it could be because contacts might be stuck in the automation flow, receiving too many emails. This could lead to emails being ignored, resulting in a lower open rate, which directly impacts your sending reputation.

  13. Use a unique subject line
    Try to avoid having the subject line of an email identical to a piece of text within the email content. If this is the case, there is a high chance that a receiving mail provider will mark it as spam.

  14. Make unsubscribing easy
    A spam marking by a recipient has a negative impact on your sending reputation. Therefore, prevent recipients from marking emails as spam by making unsubscribing as easy as possible for them. This way, they can indicate their preference to stop receiving emails by unsubscribing, instead of resorting to marking it as spam. Ensure that the unsubscribe link is clearly visible and consider placing a second unsubscribe link at the top of your email.

For more information on availability and shipping reputation, you can refer to the following help articles:

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