[sync] Horde ActiveSync with outlook 2013 problem on Centos 6.5 + apache on virtualmin

[mn 320]

Thank you for your answer.
I also tried to check if the problem is apache related by adding something
to the url and accessing it via a web browser.
Here is the server response:
<d:error><s:exception>Sabre\DAV\Exception\Forbidden</s:exception><s:message>Requested
uri (/hmail/rpc.php?Cmd=) is out of base uri
(/hmail/rpc.php/)</s:message><s:sabredav-version>1.8.10</s:sabredav-version></d:error>
Can this be the source of my problem? I get a response if I access
/hmail/rpc.php (have to login). Is it possible that outlook adds something?
Here is what I get via outlook in my httpd logs:
POST /Microsoft-Server-ActiveSync?Cmd=FolderSync&User=user at domain.com&DeviceId=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx&DeviceType=WindowsOutlook15
HTTP/1.1" 500 264 "-" "Outlook/15.0 (15.0.4641.1000; MSI; x86)
and via a browser it tells me that activesync in not available via a
browser.
Here is my .htacces
---------------------------------------
allow from all
AcceptPathInfo On
<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteCond   %{HTTPS} on
    RewriteRule .* -
[env=HTTP_MS_ASPROTOCOLVERSION:%{HTTP:Ms-Asprotocolversion}]
    RewriteRule .* - [env=HTTP_X_MS_POLICYKEY:%{HTTP:X-Ms-Policykey}]
    RewriteRule .* - [env=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
    RewriteCond   %{REQUEST_FILENAME}  !-d
    RewriteCond   %{REQUEST_FILENAME}  !-f
    RewriteRule ^(.*)$ rampage.php [QSA,L]
</IfModule>
--------------------------------------

And in httpd.conf
--------------------------------------
RedirectMatch 302 (?i)/autodiscover/autodiscover.xml
https://secure.domain2.com/autodiscover/autodiscover.xml
RedirectMatch 302 (?i)/Autodiscover/Autodiscover.xml
https://secure.domain2.com/Autodiscover/Autodiscover.xml
RedirectMatch 302 (?i)/AutoDiscover/AutoDiscover.xml
https://secure.domain2.com/autodiscover/autodiscover.xml
Alias /Microsoft-Server-ActiveSync /home/domain2/public_html/hmail/rpc.php
Alias /autodiscover/autodiscover.xml /home/domain2/public_html/hmail/rpc.php
Alias /Autodiscover/Autodiscover.xml /home/domain2/public_html/hmail/rpc.php
Alias /AutoDiscover/AutoDiscover.xml /home/domain2/public_html/hmail/rpc.php
Alias /rampage.php /home/domain2/public_html/hmail/rampage.php

(I try to sync domain.com via secure.domain2.com - ssl certs are in place
and postfix/dovecot have no problem with this config [Can it be a security
prevention while accessing the sync by horde?]).