Just had an issue with not being able to receive emails. This was down to zen.spamhaus.org which bounced emails back with a message similar to: - Took me a few hours to rectify this issue and the full credit goes to nhybgtvfr. I found this post: - https://forum.howtoforge.com/threads/solved-problem-with-zenspamhausorg.90829/#post-464393 and sure enough that cleared the issue - thanks nhybgtvfr What I did was: - 1/ ISPConfig >> System >> Server Config >> 'Mail Server Name' >> Mail 2/ Towards to bottom of the file you will find "Real-time Blackhole List" = zen.spamhaus.org 3/ Delete the above entry 4/ This should clear the issue Looks like spamhaus are on to a new get rich quick scheme!!! Once again many thanks nhybgtvfr