My mail warn log is full of this type of warnings. May 24 22:49:27 server1 postfix/smtpd[29643]: warning: 178.222.143.182: hostname 178-222-143-182.dynamic.isp.telekom.rs verification failed: No address associated with hostname May 25 00:26:57 server1 postfix/smtpd[31993]: warning: 109.167.192.248: hostname 109-167-192-248-nat-pool-gal1.westcall.net verification failed: No address associated with hostname How alarming is this and how I can get rid of this. Please help.
You can't rid this, these are connections to your smtp server. Just use fail2ban to ban brute force attacks and check if your server is an open relay. You can change the smtp standard port too, if you do this, you will avoid scanners, spamers, brute forcers and more... Cheers!
