Reduce spam probability of e-mails

Ingo Updated by Ingo

When sending e-mails, it is very important that your customers receive the e-mails sent - such as an invitation to an event or a subsequent confirmation e-mail with the corresponding QR code - in perfect condition. 

But we all know the dilemma from our own e-mail inboxes: Every day dozens of e-mails reach us, often declared as spam by e-mail clients ts, even though they are not spam. If an e-mail is declared as spam, it often ends up directly in the spam folder and not in the actual inbox. As a result, "spam e-mails" are often not even opened or read by your customers.

Unfortunately, it is not possible to define the criteria in such a way that your e-mails are one hundred percent not classified as spam by your customers' e-mail clients. However, there are certain parameters that should be considered in order to reduce the classification of your e-mails as spam as much as possible. The subject line, the preheader, attachments of your e-mails, images, but also the sender authentication and the sender reputation (quality of the e-mail platform) play an important role.

Below we have compiled some criteria for you, with the support of Mailjet.
  • Avoid terms that could be classified as spam words by your e-mail client. Often these are expressions that are intended to motivate a particular action, such as financial promises, gambling or dating offers ("free", "gift", "sale", "cash", "bill", "health", etc.).
Here you can download a checklist with spam words. Please note that this is an offer from our e-mail provider Mailjet.
  • Do not use full capitalization of all content in the subject line, preheader text, or main text and try to keep the number of words printed in red or bold as low as possible. Also, the use of several exclamation or question marks in a row or of symbols such as "€", "$", "@", etc. should be kept to a minimum.
  • The subject line of your e-mails should not be too long, ideally it should contain 35 to 50 characters. Subject lines that are too long will be marked as spam faster by the email client.
  • Do not use web-based email sender addresses such as, but always use domain-specific sender names that are linked to your website or can be associated with your company or the relevant event. The linked website (in this case the registration page for the event) should be active and reachable, otherwise the email could be considered suspicious. Ideally, the mailing email address should be added to your guests' contact list. This is especially recommended for guests you want to invite to your events on a regular basis.
  • Do not use bought, borrowed or copied contact lists from third parties, but maintain your own customer distribution list by asking for e-mail addresses when you register on your website. Update and clean up your list regularly, focus on those customers who are most interested in your events and therefore in your company's e-mails or newsletter. It is also recommended to use the double opt-in procedure, which is also offered by Sweap. These measures can help to increase the reputation of your mailing list and thus reduce the probability of spam. 
  • If you regularly send e-mails to the same guest base, it is recommended that you have the sender's e-mail address added to your guests' contact list. 
  • Find a good mix between images and text information. Our Sweap e-mail templates will help you do this. An e-mail containing only one large image file is more likely to be classified as spam.  
  • Avoid attachments in your e-mails, as they are often suspected to contain viruses. Instead, add "click here" links that take the email recipient directly to the file or article on your website. However, these should be used minimally in an email. Here, too, we support you with the e-mail templates from Sweap. This allows you to quickly and easily insert acceptance and rejection buttons in an invitation e-mail, which will forward your guests directly to the event for feedback. Alternatively, it is also possible to insert a button "Direct acceptance" or "Direct rejection" via Sweap. In this case, your guests will not be redirected to the registration form and the feedback page, but will confirm their participation or cancellation directly.
  • Send the content for which your customers have registered. Non-relevant content can be quickly marked as spam by the clients of the e-mail recipients. Furthermore, the more people open your e-mails, the better your sender reputation will be.
  • Take care to avoid spelling mistakes within your e-mails. 
A useful source for this article was the Mailjet article "How to save your emails from the spam folder" by Juliane Heise, which you can read here
Sweap offers you the possibility to use the e-mail log to see whether your e-mails were sent without errors or, for example, whether a bounce occurred. You can find more information about this in this article

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