How to prevent that bounces are blackholed?

On our domain all unrouted e-mails are blackholed with *: :blackhole: in etc/valiases/domain.com. The problem is that all bounces are send back to our hostname @hostname.domain.com and all these emails are blackholed too. I want to receive e-mail bounces. How?

What I tried:
I manually added an alias file for the hostname (etc/valiases/hostname.domain.com) with a forward to our main email box. That works without problems and I get all bounced e-mails.
Now the problem is that the alias file hostname.domain.com in etc/valiases is removed by cpanel or any script automatically every day. How can I prevent that? Where is this script? Can I change it?

 

Unrouted emails are blackholed but I want to receive emails to hostname.domain.com (they are blackholed too).

Therefore I put an valias "hostname.domain.com" in etc/valiases (with a forward to my main email box) but this alias file is deleted automatically always. Why?