One of our admins was recently blocked from posting with the following message

Your IP x.x.x.x has been blocked because it is blacklisted. For details please see https://check.spamhaus.org/listed/?searchterm=x.x.x.x

After some research, I found the this FAQ on the Spamhaus website:
https://www.spamhaus.org/resource-hub/email-security/getting-a-spamhaus-error-when-using-phpbb-heres-whats-going-on/

I have disabled the Check IP against DNS Blackhole List as a workaround on our board for now, but considering the Can you help us to contact phpBB to implement a fix? section in the above FAQ

The ultimate fix is for the phpBB software configuration to be updated to point to the FREE Spamhaus Data Query Service (DQS). This will allow queries to continue from an open resolver.

So if you work for phpBB or can support us with an introduction to help get the necessary fix made, please let us know via Twitter or LinkedIn.

I thought it would be helpful to make you guys aware of this, so you can get in touch with the Spamhaus team and hopefully get this fixed.

Thank you