My mail sender was listed at the spam blacklist for several weeks, and finall I found the solution: configured the hosts properly, and replaced the “localhost.localdomain” with ” xxx.yourdomain.com”
mailserver localhost.localdomain localhost
mailserver xxx.xxxx.com localhost
The below is the information from http://www.abuseat.org
IP Address 1xx.1xx.100.1xx is listed in the CBL. It shows signs of being infected with a spam sending trojan, malicious link or some other form of botnet.
It was last detected at 2017-04-10 12:00 GMT (+/- 30 minutes), approximately 1 days, 4 hours, 59 minutes ago.
It has been relisted following a previous removal at 2017-04-07 07:39 GMT (4 days, 8 hours, 56 minutes ago)
This IP address is HELO’ing as “localhost.localdomain” which violates the relevant standards (specifically: RFC5321).