I know there are many posts on the subject, but I did not find a solution, every time someone tries to enter my server which gives me the following log ..
Aug 21 11:37:05 postfix/smtpd[27750]: Anonymous TLS connection established from unknown[141.98.10.81]: TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)
Aug 21 11:37:05 postfix/smtpd[27750]: warning: unknown[141.98.10.81]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Aug 21 11:37:05 postfix/smtpd[27750]: disconnect from unknown[141.98.10.81] ehlo=2 starttls=1 auth=0/1 quit=1 commands=4/5
I have configured fail2ban so that they can only try once, but this machine changes its IP every 2 seconds. Is there a way to stop trying to enter? I think from trying so hard it's going to block my server since I'm sending emails