autodiscover for 2 completly different domains

Solution 1:

How did you add the domain maruna.com to your email addresses? By Email Address Policy or alternative UPN suffix?

Do you get any internal/external hostnames related with the domain maruna.com if you perform an E-mail AutoConfiguration test in Outlook?

Besides, based on the result in the Outlook, make sure the SCP and internal/external URLs/Hostnames of virtual directories aren't pointing to the domain maruna.com, you could run the following commands in the EMS to see that:

Get-OabVirtualDirectory | fl Identity, server, *Auth*, InternalURL, ExternalURL
Get-WebServicesVirtualDirectory | fl Identity, server, *Auth*, InternalURL, ExternalURL 
Get-OutlookAnywhere | fl Identity, server, *Auth*, InternalHostName, ExternalHostName 
Get-OwaVirtualDirectory | fl Identity, server, *Auth*, InternalURL, ExternalURL 
Get-ClientAccessService | fl Identity, Name, AutodiscoverServiceInternalUri 
Get-EcpVirtualDirectory| fl Identity, server, *Auth*, InternalURL, ExternalURL 
Get-ActiveSyncVirtualDirectory | fl Identity, server, *Auth*, InternalURL, ExternalURL
Get-MapiVirtualDirectory | fl Identity, server, *Auth*, InternalURL, ExternalURL 
Get-PowerShellVirtualDirectory | fl Identity, server, *Auth*, InternalURL, ExternalURL