Many customers who sent campaigns on Feb 20 reported high complaint rates. Upon further review of engagement by domain reports we are able to confirm that the complaint rates went up significantly for these email domains –,,,,

Why did this happen?

It appears there was a change in the Hotmail algorithm that determines what email go to spam folder vs. inbox. As a result, 3 things happened:

  • A very high volume of spam is been seen in the Inbox.
  • Regular senders inboxed more of their emails than they did historically, seeing higher open rates and as a result higher complaint rates.
  • Some subscribers had to mass move emails to Spam folder or marked large batches of emails as Spam, likely marking some emails as spam without high intent.

What should you do?

Consider using segmentation and exclude high complaining domains in the next 1-2 days to lower your overall complaint rates, whether you are using Amazon SES and worried about suspension or just want to avoid getting caught in the crossfires.

As always, to keep complaint rate low, follow these email deliverability best practices:

  1. Make your unsubscribe link east to see/find, don’t make the text small
  2. Consider lowering your frequency if your complaint rates are high.

To ensure you maintain high deliverability and inboxing follow best practices. If you think you already do, please review this article on advanced deliverability and inboxing tips.

If you are a BigMailer customer and need assistance or would like an audit of your account please reach out to us via chat.

We will be posting updates here if you want to know when this issue gets resolved.