Complaint Rate

Why is my e-mail showing up in spam?

When your emails don't arrive, you know something is wrong. There are then several reasons, such as using the wrong e-mail address or missing dates. Another reason that your e-mail is not arriving is that you ended up in the spam box. For transactional e-mail, this often has to do with a complaint rate that is too high. This rate is an essential indicator of your transactional email flows. Too high a complaint rate negatively affects the delivery of your emails. Within the Flowmailer dashboard, you can see a report of this complaint rate.

This article explains the concepts of the feedback loop, complaint, and complaint rate. We also describe how complaints can occur and what measures you should take.

Feedback loops and complaints

When your transactional e-mail messages are delivered to specific web-based e-mail clients of Internet Service Providers (ISP) like Outlook, Gmail, or Yahoo, the recipient can indicate that your message is 'unwanted'.

Image of a complaint rate in Flowmailer

Such a signal is fed back to Flowmailer by the relevant ISP through a so-called feedback loop. To prevent a recipient who sends such a signal from being contacted again by e-mail, Flowmailer places the e-mail address of this recipient on the filter list with the status "complaint.

Given the nature of the e-mail messages you send through the Flowmailer platform, you can expect the number of recipients who send such a signal to be negligible. To gain insight into the extent to which this is the case, Flowmailer recently started reporting the complaint rate on the dashboard. This ratio is calculated by plotting the number of complaints during a period against the number of sent email messages during that period (by default, the complaint rate is displayed for 'today').

Why does the recipient experience the transactional email as an unwanted email?

There can be several reasons why recipients may label your transactional e-mail as unwanted, and each reason requires appropriate follow-up. For almost all transactional e-mails, the recipient expects to receive an e-mail and will even take action if the e-mail is not received in the mailbox in the foreseeable future. And yet, it happens that transactional emails received result in complaints. What drives the recipient to press the 'SPAM' button? For transactional e-mail, a complaint rate above 0.03% is cause for concern and requires attention and action.

Fear of commercial follow-up emails

For starters, a recipient may want to avoid the possibility that more commercial emails will follow after that essential transactional email is received. Thus, the recipient indicates that further "emails" are undesirable. The recipient does not realize that future transactional emails will then also not be sent. For example, in the case of repeat purchases, order confirmations are not sent. From that point of view, following up on these complaints is essential.

For example, have customer service contact the recipient in question and reassure the recipient. Then ask the recipient to drag the 'unwanted' e-mail back from the junk mail folder to the inbox. This signals to the ISP that the e-mail was mistakenly labeled as 'junk'. You can then remove the recipient from the filter list in Flowmailer, and future transactional emails will be sent again to the recipient.

Your transactional email is too commercial

Transactional communication is necessary communication and then especially necessary for the recipient. It goes without saying that a transactional e-mail can be commercial. However, if you go overboard with this, it will irrevocably affect the number of complaints. Make sure the ratio service message/marketing message complies with the 80/20 rule and make sure your marketing message is relevant and consistent with your transactional message. You will notice that this approach will rarely result in complaints.


Finally, a recipient may have unintentionally pressed the 'SPAM' button. Such complaints in themselves will not result in a too high complaint rate. However, it is important to follow up on these complaints, as described earlier.