On 11/20/25 11:21, Bas v.d. Wiel via mailop wrote:
Chiming in with a "me too" but from Microsoft's Outlook cloud environment. Connection gets made, TLS handshake, then nothing from all corners of the Azure cloud both IPv4 and IPv6. I cannot receive any mail from Microsoft anymore. This has been happening here for a few months now. My own MTU is 1500, no VLAN's, tunnels or other stuff in there that would eat bytes from that. I'm now running a secondary MX from a different network, essentially the same setup but works just fine.. I'm completely stumped.
Sounds like it could possibly be due to TLS1.3 "post-quantum" keyshares. I've only seen the issue from the other side of the equation so not sure what it looks like exactly on the receiving side, but your description does trigger some "spidey-senses" for me ;)
Viktor Dukhovni explains it and how you can test for it here: https://list.sys4.de/hyperkitty/list/[email protected]/thread/ZDR54KQTAHVL35CQERXXB6NVVRR7XM42/ -- BR/Mvh. Dan Malm, Systems Engineer, one.com _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
