The short answer is:

Outlook no longer supports Autodiscovery for connecting via 
ActiveSync. You can read much about this by searching Google.  It also 
hides the ability to manually configure an ActiveSync mailbox. You can 
unhide this ability by reading:
https://support.microsoft.com/en-us/help/3189194/how-to-disable-simplified-account-creation-in-outlook


The longer answer is:
Outlook uses a v2 of the Autodiscovery protocol, that first always 
contacts microsoft's servers, which is then supposed to return either 
the url to the v1 autodiscovery service, or the url for ActiveSync.   
I've implemented support for v2 locally, but unfortunately, Outlook 
doesn't actually make a request for the "MobileSync" namespace, 
instead it uses the "outlook" namespace, which is used to configure 
outlook for NON-ActiveSync clients (IMAP, POP3, etc..). This is why 
the response you are receiving does not contain the ActiveSync URL.

Config:
$conf['activesync']['params']['driverconfig'] = 'horde';
$conf['activesync']['storage'] = 'Sql';
$conf['activesync']['enabled'] = true;
$conf['activesync']['emailsync'] = true;
$conf['activesync']['version'] = '14.1';
$conf['activesync']['auth']['type'] = 'basic';
$conf['activesync']['autodiscovery'] = 'full';
$conf['activesync']['outlookdiscovery'] = false;
$conf['activesync']['logging']['path'] = '/var/log/horde';
$conf['activesync']['logging']['level'] = '2';
$conf['activesync']['logging']['type'] = 'perdevice';
$conf['activesync']['ping']['heartbeatmin'] = 60;
$conf['activesync']['ping']['heartbeatmax'] = 2700;
$conf['activesync']['ping']['heartbeatdefault'] = 480;
$conf['activesync']['ping']['deviceping'] = true;
$conf['activesync']['ping']['waitinterval'] = 15;

Im Fiddler sieht man, dass keine URL in der Antwort enthalten ist.

Manuelle Einrichtung in OL funktioniert mit ActiveSync.

Wenn ich mit wget die autodiscover.xml hole enthält diese die Serverangaben.

Request/Response aus Fiddler-Mittschnitt während Outlook Autodiscover-Test:

POST 
https://autodiscover.tom-friedrich.de/autodiscover/autodiscover.xml 
HTTP/1.1
Cache-Control: no-cache
Connection: Keep-Alive
Pragma: no-cache
Content-Type: text/xml
User-Agent: Microsoft Office/16.0 (Windows NT 10.0; Microsoft Outlook 
16.0.10352; Pro)
X-MS-CookieUri-Requested: t
X-FeatureVersion: 1
Client-Request-Id: {3C5F35C5-3832-43CB-BE01-9C607192CB7B}
X-User-Identity: tom@tom-friedrich.de
X-MapiHttpCapability: 1
Depth: 0
X-AnchorMailbox: tom@tom-friedrich.de
Content-Length: 353
Host: autodiscover.tom-friedrich.de
Authorization: Basic ?????????????????????????????????????
Cookie: OutlookSession="{6258E938-8B9C-4FF6-AB50-0B1D104D7088}"; 
PHPSESSID=73g28ua8hmdlpipmskbuq53fn6; 
PHPSESSID=il9rsdu32ba8omc796p4i886e7; 
horde_secret_key=???????????????????????

<?xml version="1.0" encoding="utf-8"?><Autodiscover 
xmlns="http://schemas.microsoft.com/exchange/autodiscover/outlook/requestschema/2006"><Request><EMailAddress>tom@tom-friedrich.de</EMailAddress><AcceptableResponseSchema>http://schemas.microsoft.com/exchange/autodiscover/outlook/responseschema/2006a</AcceptableResponseSchema></Request></Autodiscover>


HTTP/1.1 200 OK
Date: Thu, 28 Nov 2019 19:10:19 GMT
Server: Apache/2.4.25 (Univention)
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: private, max-age=10800
Last-Modified: Sun, 18 Dec 2016 21:01:07 GMT
Content-Length: 514
Vary: Accept-Encoding
Content-Type: text/xml;charset=UTF-8
Set-Cookie: PHPSESSID=73g28ua8hmdlpipmskbuq53fn6; path=/
Set-Cookie: PHPSESSID=00dj1fj353tfas972dhj3obtg1; path=/
Set-Cookie: default_horde_view=deleted; expires=Thu, 01-Jan-1970 
00:00:01 GMT; Max-Age=0; path=/; domain=autodiscover.tom-friedrich.de
Via: 1.1 autodiscover.tom-friedrich.de
Keep-Alive: timeout=5, max=99
Connection: Keep-Alive

<Autodiscover 
xmlns="http://schemas.microsoft.com/exchange/autodiscover/responseschema/2006">
                 <Response 
xmlns="http://schemas.microsoft.com/exchange/autodiscover/outlook/responseschema/2006a">
                 <User>
                     <DisplayName>Thomas Friedrich</DisplayName>
                 </User>
                 <Account>
                     <AccountType>email</AccountType>
                     <Action>settings</Action></Account>
                 </Response>
                 </Autodiscover>