Hi Twisted,
The domain policy information says
"If your delivery server cannot send emails to certain domains, or it can only send to a small list of domains, you can add domain policies to reflect this. If you want to send emails only to yahoo.com but deny for any other domain, you will need a allow policy for the domain yahoo.com and a deny policy on domain * If you want to send to all domains except yahoo, then a deny policy on yahoo domain is enough. If you want a policy for all yahoo emails, including yahoo.co.uk, yahoo.com.br, etc you can simply enter "yahoo" as policy domain. The sign * acts as a policy wildcard matching any domain. A domain of domain*.com or *domain.com has no effect."
If I create two delivery servers one for all domain but deny yahoo/aol and 2nd server to allow yahoo/aol and deny all of others. Then I attach both of the servers in my campaign - would Mailwizz attempt the delivery of yahoo/aol on both the servers and then only send from 2nd.
Or in case if yahoo/aol attempted from 1st but denied (because of domain policy) it would simply drop the email attempt.