Super simple AutoDiscover test. Does not attempt to encapsulate all of Outlook's logic.

Test-AutoDiscover.ps1

[CmdletBinding()]
param (
    [Parameter()]
    [string]
    $HostName,

    [Parameter()]
    [string]
    $EmailAddress
)

$body = '<?xml version="1.0" encoding="utf-8"?><Autodiscover xmlns="http://schemas.microsoft.com/exchange/autodiscover/outlook/requestschema/2006"><Request><EMailAddress>' + $EmailAddress + '</EMailAddress><AcceptableResponseSchema>http://schemas.microsoft.com/exchange/autodiscover/outlook/responseschema/2006a</AcceptableResponseSchema></Request></Autodiscover>'
$response = Invoke-WebRequest "https://$HostName/autodiscover/autodiscover.xml" -Method POST -ContentType "text/xml" -Body $body -UseDefaultCredentials
if ($response.StatusCode -eq 200) {
    $response.Content
} else {
    $response
}