Hi,
I understand that you're using a single NIC deployment on your Expressway-E? You've mentioned that you're doing NAT reflect, you only do that when you use a single NIC.
Anyway, you didn't provide much of information.
- Is the MRA zone from Expressway-C to Expressway-E is up?
- Do you see any ports being blocked in the Firewall?
- Did you publish the "_collab-edge._tls.domain.com" SRV record in the public DNS?
- Did you create an internal DNS A Record in your internal DNS server that is pointing to the PUBLIC IP address of the Expressway-E?
- Did you create a PTR record in your internal DNS server that points the PUBLIC IP address of the Expressway-E to its FQDN? (without it won't work, starting from Expressway 8.8.x)
- Is Jabber working fine in the corporate LAN?
Please check all the above.
If all the above are fine, please go and on both of the Expressway server and do: Maintenance -> Diagnostics -> Diagnostic logging, and press "Start new log". After you do that, try to make a login with a Jabber device over the internet and after you get your error press on "Stop logging" and gather both logs and attach them here.