can't configure outlook outside of network (outlook anywhere) and error in MS connectivity analyzer

Greetings,
I am unable to connect Outlook to a 2016 Exchange server from outside of the network. I keep getting prompted for a password even though I entered that during the initial config. Not sure if the info below is related but wanted to add it here.

When using the MS remote connectivity analyzer, I get this:
Attempting to test potential Autodiscover URL https://domain.com:443/Autodiscover/Autodiscover.xmlTesting of this potential Autodiscover URL failed.
I also get the following failure:
The Microsoft Connectivity Analyzer is attempting to retrieve an XML Autodiscover response from URL https://domain.com:443/Autodiscover/Autodiscover.xml for user user@domain.com.The Microsoft Connectivity Analyzer failed to obtain an Autodiscover XML response.
I think this is expected since this is testing against our third-party managed website not the exchange server. 

However, a little further down I get this:
Attempting to test potential Autodiscover URL https://autodiscover.domain.com:443/Autodiscover/Autodiscover.xmlTesting of the Autodiscover URL was successful.
Everything below this in the analyzer passes / has green check marks.

We are migrating to Office 365 next week so started running checks and ran into this. Not sure if this can be ignored but if not, I am unsure how to fix it. Don't deal with Exchange servers much anymore.

Thanks for any help.