disable autoconfig of email

I have a few customers on myserver that has email elsewhere.
so then is the question how to stop outlook and other mailprograms asking for https:/domainname/autodiscover/autodiscover.xml

or maybe i should say how do I tell my webserver to not reply to this query, since the second in the list i sto ask https://autodiscover.domaninname/autodiscover/autodiscover.xml

the second one works as intended but since all webservers on my server with virtualmin replys back with settings for imap and smtp on my server, but since there is no mail on my server it becomes wrong. since the mail is elsewhere, like on exchange online, or who ever they choos to use email from, its even a problem if they have their own inhouse exchange server