The short answer is no.
The long answer is that if your domain name is being used for a web site on another server then you will be unable to use that domain name with our mailman services. However, you can use a sub-domain based off of your domain name such as list.yourdomain.com or mailman.yourdomain.com. You can use any sub-domain you want. You will need to have your web hosting company set up an A record in their DNS server for the sub-domain and point it to our mailman server. We will give you the IP address to point it to after we receive your order.
If we are not hosting your web site, then please let us know what we can do to gain your site hosting as well. We offer a generous discount to those who are mailman clients.