Already a while ago, I got an email that my server is on the blocklist of spamhaus (here the original message: “Ihr Server befindet sich aktuell auf der CBL-Blockliste von Spamhaus.”) I even wasn’t aware that blocklists exist. Neither I was aware of spamhaus. I really couldn’t get my head around this one, especially after I read that my server is possibly emitting spam. At least I managed today to make a CBL lookup at https://www.abuseat.org . Which was positive (Begin of the original message below).
Results of Lookup
18.104.22.168 is listed
This IP address was detected and listed 256 times in the past 28 days, and 10 times in the past 24 hours. The most recent detection was at Mon Jan 27 12:15:00 2020 UTC +/- 5 minutes
This IP is infected (or NATting for a computer that is infected) with an infection that is emitting spam.
22.214.171.124 was found to be using the following name as the HELO/EHLO parameter during connections: “localhost.localdomain”.