Hi, I am currently running OpenBSD 4.0 as a greylisting server. We have found that many Microsoft Mail Servers/Mail Marshal cannot get past the greylisting. On further investigation, we found out that the MS Mail servers send a NOOP before they start sending other SMTP commands and spamd returns a 451 even for a NOOP causing the SMTP connection to terminate and the connecting mail server doesn't even get greylisted, since it hasn't even sent a "MAIL FROM" and "RCPT TO".
I've seen no mention of this in the archives, so was wondering if this is intended and if there is a permanent fix for this. We've temporarily patched spamd.c, so that spamd does nothing on a NOOP command as required by the SMTP RFC and we've seen that the MS Mail servers get properly greylisted and subsequently whitelisted. Sid
