Hi,
I have a hybrid deployment set up, and everything I've tested (thus far) is working except for mail transport from O365 to OnPrem. This is increasingly becoming a problem because it seems that MS does not use MX records to deliver mail from other O365 subscribers. Instead it is trying to use the Hybrid Deployment to deliver mail. I'm curious how this works. I thought the transporting was configured to look like it was coming from from another Exchange server in the organization, so the Default FrontEnd receive connectors would be used. Perhaps that's not the case.
On the O365 side, I see this defer error:
Reason: [{LED=450 4.4.101 Proxy session setup failed on Frontend with '441 4.4.1 Error encountered while communicating with primary target IP address: "Failed to connect. Winsock error code: 10061, Win32 error code: 10061." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or On my hybrid config, ClientAccesServers and EdgeTransportServers are null. ReceivingTransportServers are the names of two CAS servers onprem (let's say FE01 and FE02). These servers have no external A records. OnPremisesSmartHost is webmail.domain.com, which does have an external presence. Externally originating traffic from MS data center IP's to port 25 of webmail gets sent straight to the internal NLB IP for those two CAS servers (FE01 and FE02) via firewall and F5 rules.
If it doesn't look like an Exchange server, then I'd imagine I need to build a new receive connector that allows anonymous relaying from MS datacenter IP's on a new IP address that I could add to the NLB. Then route traffic there via the F5 virtual server. Any thoughts about what the issue could be?