A followup on this - when trying to reproduce the problem today running smtpd with tracing enabled (-T smtp), the test messages with dots in the local part, sent from the same machine and mail client, were accepted with no fuss at all.
So it appears this was a heisenbug. Even more so in that turning the tracing off did not lead to any difference at all in message accept and delivery. So basically this is not worth spending any time on, unless of course you see something similar with your own setup. All the best, Peter -- Peter N. M. Hansteen, member of the first RFC 1149 implementation team https://nxdomain.no/~peter/blogposts https://nostarch.com/book-of-pf-4th-edition "Remember to set the evil bit on all malicious network traffic" delilah spamd[29949]: 85.152.224.147: disconnected after 42673 seconds.
