On Tue, 24 Jul 2018 21:10:01 -0700 (MST) chuckee wrote: > As an ESP we can confirm that it is extremely common for ESP's to > strip out 'Received from' headers - if we didn't, then many recipient > mail servers reject emails because they look at the (often bad) > reputation of the IP address of the sender and judge an email on > that.
I don't find it to be all that common. Where I have seen it, the ESP has cited privacy as the reason. > For example, if a sender is sending an email from a hotel, > their email would be judged based on the reputation of the hotel's IP > address (which is a ridiculous scenario). We can confirm that > Barracuda is one such email filter that does this. Barracuda is based on SpamAssassin, and I would guess it's still handling this the same way as SA, and the way it did when a disgruntled employee posted their rules some years ago. Deep tests look for the open proxies/relays, static IP addresses of hacked servers and IP blocks allocated to spammers. If a spammer controlled address submits to a service provider there's a good chance its spam. By the look of it the only really high scoring deep rule is the Spamhaus snowshoe list, which is pretty reliable.
