That is possible. Happens often, mostly on VPS servers with Spamhaus.
Best is to use the below link, check your ip and the request delisting. Be sure to state in the message that you are a new owner of the ip.
No guarantees. We had an issue from an old spam ip too. When we got it and used a new domain name on it, there was no way of getting it of Spamhaus list.
You can block the website from being sent. accept only authenticated.
In whm/cpanel you have the option to not send emails as apache
what did you suggest?
Authenticated mail only is an option. Except for disabling normal mail in the Firewall, I don't know how it can be done in DA. It must be possible some way, but I don't know how.
You have a thread about that, so probably you have to wait until somebody answers the thread. Or if you're in a hurry, send in a ticket.