On 19 Apr 2016, at 9:29, jaso...@mail-central.com wrote:
Mainly I just want to make sure I've not missed or misconfigured something, and that this is just business as normal.
It's pretty much "business as normal" but the pointless noise can be reduced with "postscreen_greet_action = drop" and reduced even further with something like fail2ban that watches logs and blocks IPs that trigger the PREGREET check. Many years ago there were a handful of legitimate(ish) bulk mail senders who spoke too fast as an optimization but as far as I can tell, none have done so since before postscreen existed. The Sendmail GreetPause feature effectively cleared out all the significant false positives a decade ago. No one will ever come to you asking why you rejected mail offered in a fast-talking session because at this point the only fast-talking SMTP clients are malware. There are occasional short-lived cases of compromised mail servers and NAT devices giving the same IP to traffic from infected machines and mail servers, so there is some collateral damage possible with drop+block, but it is rare and transient (as long as you don't drop+block+forget.)
