I've been getting this since a few weeks ago:
Transcript of session follows. Out: 220 www.example.com ESMTP In: EHLO Out: 501 Syntax: EHLO hostname In: HELO Out: 501 Syntax: HELO hostname In: QUIT Out: 221 2.0.0 Bye For other details, see the local mail logfile
These connections come from all the internet, from 18.104.22.168/8 to 22.214.171.124/8
My question is NOT how to stop it (-j DROP --dport 25) or how to stop receiving the mails (remove protocol in postfix main.cf)
My question is simple: why? is it a misconfigured bot? I googled and saw messages related to this since 2006. I get 30 of these a day or more. I'm waaaay curious about this. Anybody has more information about it? when did it begin? what's going on?
That's all, thank you.