You seem to have redacted the relevant information, for no apparent good reason. To stand any chance of helping (apart from the guidance already given) we’d need to know who your provider was, but you’ve obfuscated the addresses of their system and proxy.
However, I’d ask:
Why do you have a proxy if its name is the same as the host (assuming the different number of Xs is not significant)?
Why does the host name begin with Proxy- ?
Also, unlikely to be causing your problems here, but:
Why are you using a deprecated channel driver?
Why do you need insecure=port?
Why have you set defaultuser (under a deprecated name) when the registration isn’t inbound?
My guess is that either host or fromdomain are wrong.