The Science mailservice used Spamhaus for decades as one of the blocklists to filter spam in mail.

When we were notified that we would need a commercial license that would cost ca. 5kEUR/y, we investigated how much more spam would come through without the Spamhaus service. This showed that users would get more spam, but most of it would be delivered in the Spam folder. Next to that, we expect that the spam filtering of the also used Exchange Online Protection will improve.

Therefore we stopped using Spamhaus at the end of April 2024. If many users complain about spam getting through, we can always reconsider this decision.