I'll add one in for Proofpoint's Dynamic Reputation product. Just bumped into it today. I brought up a new mail server with VULTR a few weeks ago. I just started using it for email yesterday.
Proofpoint seems to have a block unless known scheme of some kind. I've started a ticket with them. I have reverse DNS, SPF, DMARC, and DKIM setup. The mxtoolbox.com didn't show any active IP blocks. I'm wondering if Proofpoint blocks all IPs until someone starts a case to get on the white list. Maybe they develop a white list from some insight they have into legitimate MTAs. On Friday, August 1, 2025 8:48:22 PM CDT [email protected] wrote: > Greetings Peter! > > I've had no issues with Gmail generally, but I have had infinite > troubles with Outlook. Although the DKIM signature appears valid to > Gmail and other providers, Outlook insists that my mail has an invalid > DKIM signature. I can't remember the last time Outlook.com has not > marked email from my domain as spam. But the mail generally gets into > Gmail's inbox just fine. > > PS: Thanks for your Book of PF! That and your free guide floating around > on the Internet has been a big help to me. > > > This message is the start of an effort to research just how the BIG MAIL > > operators treat SMTP mail from small outfits like nxdomain.no and friends. > > > > We have seen GOOG and to a lesser extent MSFT, YHOO mail exchangers seem > > to > > accept messages from our domains for delivery, only to have them not turn > > up in the intended inboxes after all or at best land in the users spam > > folders. > > > > I am pondering starting a campaign to collect war stories with as much log > > data and other relevant data as possible in order to write an article > > which may evolve to something else. > > > > If you have a story along those lines that you can back up with actual > > data > > that you are allowed to share, I want to hear from you. Even "for your > > eyes > > only" sharing can be useful as background or context. > > > > All the best, > > Peter
