Some of my clients use Google’s offerings, especially for email. One client in particular kept reporting that some of their emails were being blocked with 553 sorry, your envelope sender is in my badmail list. (#5.7.1) results. We thought it was something in our configuration and reviewed the SPF, DKIM and DMARC settings, but found not issues. Eventually we got through to a Google support rep, who initially claimed it was our configuration, but eventually admitted that some of their outgoing IPs are on real time black hole lists.

For an organization the size of Google’s mail system, it is impossible that spam isn’t being delivered all the time. However, it has been months and we still get these blocks with alarming regularity. To be clear, it only happens with some very large organizations that we send to and it is their choice to subscribe to lists as aggressive as this. Generally resending later that day will succeed (because the IP for the outbound mail is different), but the users don’t understand why and want it “fixed”.

I’m curious if other major players are being blocked in this manner: when I searched for others having similar issues I found surprisingly few results.