need a trick how to setup mail following way

[next-step]

Hi All

I need a trick

I have different domains, they are not aliases.
www.businesolymp1.com
www.busolymp2.com
www.bolymp3.com
etc

but I need to setup their mail service like they are aliases:
so
acc1@businesolymp1.com
acc1@busolymp2.com
acc1@bolymp3.com

all will be received at general account acc1@businesolymp1.com

I tried to setup domain alias busolymp2.com for businesolymp1.com for Mail service only but it says that domain name already exists.

Im sure it can be done very simple in qmail settings. but how?