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Sending emails is not an exact science and several factors can cause you to, sometimes, face some deliverability problems. 

Here, we will speak about some of the reasons you might have deliverability issues and we will also offer you our solutions and best practices. When applying these solutions, please bear in mind that the improvements will not be felt overnight, and may take a significant amount of time before they produce satisfying results.

Spam Inbox

Your emails may be ending up in the spam folder if you see the following cases:

    • low open rates compared to the average open rate, or

    • large deviations between mail provider for the same campaign,

    • Low open rate and low bounce rate

    • Decrease open rate overtime on the same provider

To fix this scenario, you will need to rebuild your reputation with the mail provider that is showing you some of the problems above.

As a first step to prevent further problems, you need to exclude all contacts from the affected domains from your everyday marketing campaigns and set up a different approach only for those contacts. In order to understand why the ISP filters your emails you can check the following:

  • Have you sent high volumes to non-engaged contacts for that domain?

  • Have you changed the sending volume to that domain and.or campaigns?

  • Are you getting a high number of bounces from that domain?

  • Do you have complaints coming from that domain?

If your answer is yes to any of the above questions, you can formulate a strategy to win back the trust of your contacts – and with this the trust of the ISP.

You have engagement issues

As a general rule of thumb, your reputation can be improved if you focus on your contacts who are already engaged. Create a segment that contains all contacts from a particular domain who have responded to any of your marketing emails in the past 90 days. Anyone else from the same domain should be excluded until you gain back your reputation. Once you see your open rates improving, you can increase the target segment. For example, you can modify the segment criteria to contain all contacts who have engaged with your emails in the last 180 days. Once your reputation is back to normal, you can start sending again without strict exclusions.

You are sending to spam traps

The other reason for being put into spam folders is if you send to spam traps. There are two types of spam traps:

  • Recycled email addresses – Recycled spam traps are email addresses that once belonged to an actual person but have been abandoned for a while. ISPs turn these mailboxes into spam traps, which means that the mailbox still exists (so you will not see any bounces), but belong to the ISP rather than to a person. They are used to catch senders that do not use industry best practices such as keeping a healthy database by regularly removing bounced or non-engaged contacts.

  • Artificial email addresses – ISPs and spam blocklist providers also create their own fake email accounts that have never belonged to any person (and have therefore never subscribed to any marketing mailing). These are meant to catch senders that buy address lists.

There are multiple reasons for hitting spam traps:

  • Your data capture points are not carefully set up, for example, you do not use double opt-in (DOI), an email validation tool, or captcha.

  • You try to send to a contact base that is old/bad or has not been verified in the last year.

  • You do not clean up your database of bounces and inactive contacts frequently.

  • You revalidate bounced email addresses every now and then without understanding the bounce reasons.

  • You buy address lists.

How to fix it?

The best solution to avoid Spam Traps is to add an email validation tool, a captcha, and, where possible, a Double Opt-in for your acquisition process. You should also cleanse your database regularly and, of course, send to contacts that are active/engaged with your program. This way you avoid sending to old/bad data. 

Your contacts are complaining about unwanted emails

If you are constantly sending unwanted emails to your contacts, at some point they will be so frustrated that they will complain about you. Once someone hits the “Report as spam” button the ISP will bounce the message before it reaches the inbox or it will be marked as spam and be placed on the spam folder. A spam complaint rate above 0.2% is considered high.

If you want to regain your good reputation, your first task is to have a clear overview of how you capture and manage contact data, especially on the opt-in process. Once these workflows are clear and regular checks are set up, you can move forward to improve your content.

You have content-related spam scoring

The other common issue for bad spam scoring is your content. There are no clear boundaries or rules that have the same effect on all ISPs, but there are some general industry best practices (such as testing your content and subject lines, image size, link tracking, amongst others) that should be followed and can help you to create more engaging content that will lead to better engagement and better deliverability results. 

The SAP Emarsys Deliverability Advisor also gives you a number of insights while you are building your email campaign and it is also available from the Deliverability Report. If you have problems with engagement and spam folders, you should check the results for your content and make sure you don’t have any warnings in this regard.


Bounces are emails that indicate that a campaign could not be delivered to certain contacts.

There are three types of bounces:

Soft Bounces

Emails could not be delivered because of temporary problems, such as:

  • The mailbox of the recipient is full.

  • The denoted domain cannot be reached temporarily or the host is unknown.

  • Temporary server breakdowns.

Hard Bounces

Emails could not be delivered because of permanent problems. A typical reason is that the email address does not exist ("contact unknown"). This often happens when either the contact name or the domain name have been misspelled (e.g. the email address is spelled as or

Block (Reputational) bounces

Emails could not be delivered because they were blocked by spam filters. Reasons for this could be:

  • Content with suspicious words; emails that contain inappropriate words (in the text body, the subject line, or the sender field) are usually rejected.

  • The HTML format in the sent email differs significantly from the HTML standard.

  • A recipient activated a spam filter and has put the sender on its personal spam list.

  • The sender is blocklisted, which means that the contact has informed their internet provider that they consider the email received to be spam.

  • Emails are rejected by the recipient’s server firewall (especially company servers).

How to identify and fix the issue?

In the case of the soft bounces it might be the case that, due to the fact that these are, temporary blocks, you stop sending to these contacts for a few sends and retry it in a couple of weeks. Do you have how to see the bounce code? Usually, the providers, on their postmaster pages, can provide you with a list of the bounce code and the reason for it.

In the case of the hard bounces, the best solution is for you to check the acquisition you are using. The bounces are related to a permanent error and this can happen when the domain is added to your database. If you use a Double Opt-In process, or at the minimum, you have an email authentication tool and a captcha, the possibilities of having these bad emails in your database are a lot lower.

In the case of the block bounces, as mentioned above, this is in most of the cases, related to the reputation of either:

  • Your sender domain

  • Your IPs

  • Your email campaigns content (subject lines, content, images, etc.)

Test them to guarantee that all is ok.

In this article, we have covered causes and practical solutions for deliverability problems. The main one to remember is to keep your database clean and keep active contacts at the heart of your marketing program. And please remember that improvements take time. Focus on these simple steps and you will see your delivery and inbox rates improve.

What’s next?

Please leave feedback below and/or hit the “like” button to show this type of content is useful.

You can ask questions and provide suggestions for helpful email deliverability topics in the Q&A area Q&A – SAP Emarsys Email Deliverability.

And if you’d like to find out more SAP Emarsys, you can visit the community page: SAP Emarsys CX.