Orbi not working with work email(Exchange Server)

[DwierMcIntyre]

I have installed the Orbi RBR50 at my office and all third party emails work and our company email does not and when i am at home my work email works fine on my home wifi. So i decided to troubleshoot with the firewall team and we got some information.

From what we've been able to gather so far:
1. The SYN packet comes from the wifi (public IP 204.101.3.179) address and reaches the firewall
2. The firewall takes the packet, NATing it to the internal IP of the exchange server (10.20.XXX.XX:443)
3. Firewall sends the SYNACK packet back from 10.20.XXX.XXX:443, NATing back to the exchange server's external (204.101.3.180) address
4. We assume (for now) that the device at 204.101.3.179(Orbi Router) receives the SYNACK packet (This is being investigated further)
5. The device sends us a Reset packet, attempting to have the SYNACK resent
6. This continues in a loop with 204.101.3.179 resetting the connection and exchange resending the SYNACK

Is it possible to check that the device that the Orbi RBR50 (204.101.3..179) is allowing inbound connections from our Exchange Server's external IP range(204.101.3.178/255.255.255.240)? This would help narrow down this issue even further. Thanks.

[st_shaw]

Sounds like Orbi is not your internet gateway, and it sounds like you have another router (you call it "firewall") between your ISP and your Orbi and Exchange server.

The problem sounds like the classic "hairpin NAT" issue which means your router/DNS is not setup properly to allow clients inside your Orbi LAN to access your maill server (also inside your LAN) via the mail server's external domain name ("mail.company.com") as you would enter in your email client configuration.

The fix depends on the topology of how things are wired to your firewall router, and whether Orbi is an isolated network.  Might be fixable by properly setting up hairpin NAT on the firewall, or with an internal DNS entry aliasing your mail server's domain name to the internal IP.  Your topology is not clear though.  A diagram would be necessary to understand it.

You can probably solve this by simply running Orbi in Access Point mode.

[FURRYe38]

https://community.netgear.com/t5/Orbi/My-work-emails-never-gets-sent-or-recieved-when-i-am-on-the/td...