Hi there, I have an on-premise Exchange 2013 server published via WAF and have recently begun running into an issue with Outlook 2016 clients on the internal network.
When the Outlook client attempts to locate its configuration via AutoDiscover, the request ends up being intercepted by the UTM regardless of client proxy settings (and exclusions). UTM then refuses the connection request with an HTTP/1.1 502 Invalid argument error.
I have configured Proxy Auto Configuration with the relevant details to ensure direct connection to the internal server, however this has no effect on the Outlook client. I have also configured a Web Protection exception to skip all checks for our domain and this also has no effect.
What could be causing the "invalid argument" error, or is there any way to bypass the proxy entirely for the host autodiscover.mydomain.com?
Any guidance will be greatly appreciated.
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