dnscog mail test gives false positives due to flaw in testing method

I just tested my own domain and received a report telling me my mailserver does not accept MAIL FROM:<>

This is incorrect, and looking at my log I found:

Oct 16 15:58:15 mail postfix/postscreen[4422]: PREGREET 16 after 0.5 from 216.146.46.136: HELO http://dnscog.com?

Meaning the tester triggered the "pregreeting" detection in Postfix - the tester sent SMTP commands before my server finished sending the SMTP banner.

This should be fixed.