Outlook 2016 ignores autodiscover.xml uses user@domain.com instead of user.domain

I would like to have the autodiscover function running for outlook 2016 to skip the the nag screen of fresh outlook 2016 installments.
Currently, Outlook seems to ignore the autodiscover script and uses user@domain.com instead of user.domain it seems.

At least the failed login attempt looks like that:

dovecot: imap-login: Disconnected (auth failed, 1 attempts in 5 secs): user=hello@testdomain.com, method=PLAIN, rip=4x.xx.xxx.xx, lip=5x.xxx.xxx.xxx, TLS: Disconnected, session=

I have set up the Autodiscover function on a Debian system running Virtualmin 6.03
because some client needs to set up new computers with Outlook 2016.
This leads to a nag screen which you can only skip by going into the system settings
instead which is not desired for a standard user.

if I check the testdomain.com/autodiscover/autodiscover.xml set via the autoconfig script it looks fine to me:



email settings IMAP 24 server.mydomain.com 143 hello.testdomain off no on SMTP 24 server.mydomain.com 25 hello.testdomain off tls on

Workaround for the nag screen problem to set up a user account manually:

german win 10 but you should get the idea :wink:

Current System:
Debian Linux 7
Webmin version 1.890
Virtualmin version 6.03

thanks for any help