Requests to AppDomain defined domains from classic Outlook event handler are blocked

[mserveApplied]

We have an Outlook add-in that defines some URLs used to support event based activation features in its manifest like so:

...
<ExtensionPoint xsi:type="LaunchEvent">
							<LaunchEvents>
								<LaunchEvent Type="OnMessageSend" FunctionName="onSendValidation"
									SendMode="SoftBlock" />
								<LaunchEvent Type="OnMessageAttachmentsChanged" FunctionName="onAttachmentsChanged" />
							</LaunchEvents>
...
<bt:Urls>
					<bt:Url id="Commands.Url"
						DefaultValue="https://{our_domain_here}/ui/outlook/commands.html" />
					<bt:Url id="Taskpane.Url"
						DefaultValue="https://{our_domain_here}/ui/outlook/index.html" />
					<bt:Url id="WebViewRuntime.Url"
						DefaultValue="https://{our_domain_here}/ui/outlook/commands.html" />
					<!-- Entry needed for classic Outlook on Windows. -->
					<bt:Url id="JSRuntime.Url"
						DefaultValue="https://{our_domain_here}/ui/outlook/launchevent.js" />
				</bt:Urls>

We then define the WebApplicationInfo element.

<WebApplicationInfo>
				<Id>{our_registered_app_id}</Id>
				<Resource>api://{our_domain_here}/{our_registered_app_id}</Resource>
				<Scopes>
					<Scope>User.Read</Scope>
					<Scope>access_as_user</Scope>
					<Scope>profile</Scope>
					<Scope>openid</Scope>
				</Scopes>
			</WebApplicationInfo>

Our manifest also contains a list of AppDomain elements that are allowed to be called.

In new Outlook we expect commands.html to handle events like taking action after sending an email. This works as expected and requests to the addresses defined by AppDomain elements are not blocked when made from this context. We expect the same workflow in classic Outlook to be handled by launchevent.js. However, we are noticing that requests made from this file are blocked to all domains aside from the domain the handler file is running in. For example, requests made to https://{our_domain_here}/some_path from the launchevent.js file will not be blocked but a request to https://{separate_domain_from_AppDomain_element}/some_other_path is blocked.

The options we're aware of to debug the classic Outlook portion are pretty limited. We've enabled runtime debugging and are logging the results of requests made. Unfortunately, we are seeing a very generic "network request failed" message in the response. Our assumption is that its a CORS issue since requests are not blocked when the handler origin matches the request domain. If this is the case, does classic Outlook ignore the AppDomain elements from the manifest and only allow same origin requests?