The redacted screenshot at https://nxdomain.no/~peter/blogpix/likely_suspicious.jpg https://nxdomain.no/~peter/blogpix/likely_suspicious.jpg indicates that the

The redacted screenshot at https://nxdomain.no/~peter/blogpix/likely_suspicious.jpg https://nxdomain.no/~peter/blogpix/likely_suspicious.jpg indicates that the sending server used an IPv6 address that ends with the digits 19. The SPF record for bsdly.net includes two IPv6 addresses, neither of them ends with 19. It also includes some more things, up to three layers of indirection so I'm not sure I checked everything, but I didn't see …19 anywhere. I suspect that what we have here is a misconfiguration at bsdly.net and perhaps a poorly chosen error message at gmail.