Well of course I don't know your users, but I think we need to let go of the thought that Google et al are too big to block. I've implemented radical rate limiting for the Google outgoing servers that handle group notifications (they get a 4 hour IP block from fail2ban when detected as spamming). This limits the load on the mail server significantly and has not really affected users who actually subscribed to groups (those groups are whitelisted quickly).
Google mail users need to realize that they use a crappy mail service. Cheers, Hans-Martin Am 19. August 2025 14:54:26 schrieb Jarland Donnell via mailop <mailop@mailop.org>: > Tonight we faced what can only be described as a DDOS attack from > Microsoft and Google, with a bit of IONOS sprinkled in. This is an > incredibly effective attack vector because most of us simply cannot > afford the pushback from customers if we so much as rate limit inbound > email from either Google or Microsoft. Rejecting email in an attack is > easy, but processing it rapidly at scale is quite taxing on smaller mail > infrastructure. Let me show you what this looks ilke with only a small > portion of the logs (censored, of course): https://mxbin.io/ZNuVC3 > > Basically, the attack goes like this: > 1. Set MX to target > 2. Create a wealth of freemail accounts > 3. Set all of those freemail accounts to forwarders that reject all > inbound mail > 4. Enjoy the barrage of bounce emails sent from freemail systems to > target MX > > At least in our part of this field we can't block Google or Microsoft > without users considering us to be effectively down. Can't rate limit > without them considering us to be faulty. Can't take it lying down when > Google alone is causing almost exactly 100 server load (not including > that of the others). > > Getting tough out here my friends. I have no worthwhile solutions other > than "add more infrastructure" so I wanted to share the wealth before > someone else gets caught with their pants down on this. > > <3 > Jarland > MXroute Admin > _______________________________________________ > mailop mailing list > mailop@mailop.org > https://list.mailop.org/listinfo/mailop
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