A final followup on this issue - I wrote a (relatively) short piece on greylisting vs domains with multiple outbound SMTP servers, which includes the little script I use to create a nospamd from a list of domains, of course by feeding to 'smtpctl spf walk'.
You can find the article at https://bsdly.blogspot.com/2018/11/goodness-enumerated-by-robots-or.html - TL;DR: don't download *my* nospamd, use smtpctl to generate your own :) All the best, Peter -- Peter N. M. Hansteen, member of the first RFC 1149 implementation team http://bsdly.blogspot.com/ http://www.bsdly.net/ http://www.nuug.no/ "Remember to set the evil bit on all malicious network traffic" delilah spamd[29949]: 85.152.224.147: disconnected after 42673 seconds.
