Autodiscovery outlook 2016 not working for secondary domain on exchange 2010 sp3 SBS2011.

setup:

SBS2011, exchange 2010 with sp3.
internal domain: domain1.local
external domain: domain1.eu
external dns a records
remote.domain1.eu   external ip (godady certificate is on this one)
mail.domain1.eu   external ip
autodiscover.domain1.eu external ip

configuring outlook 2016 with just email address and password works fine.

Now there is a second domain on the same box where autoconfigure does not work all the time
It hangs ons searching email server settings right after a certificate error (which is understandable cause it belong the domain above)

external dns a records
remote.domain2.eu   external ip (godady certificate is on this one)
mail.domain2.eu   external ip
autodiscover.domain2.eu external ip

After writing this question and leaving the search open after 15 minutes plus I do het a user name password question and outlook is configured.
Strange! help much appreciated!

Thanks, Tom.