I said "sending server", not "domain of the sender". If an e-mail from y...@rhsoft.net is sent by 95.129.202.170, your mid is expected to include either @blah. sunshine.at or @[95.129.202.170].
If the same mid includes @yahoo.com, for example, then the message is rejected as spam, because the IP is denied by yahoo's SPF RR. Sent from ProtonMail Mobile
