You would have to find a mailing list host and point the MX records at that particular host. So yes, it's possible to have both your site here, and a mailing list host pointing elsewhere. That's the beauty of using the records directly rather than having users use our DNS servers.
If you've got control of your DNS config (as I believe you do, such that you can control the records), you'd just have to find somewhere that handles a mailing list, and you have to set the MX Records to the IP. I don't really know a ton about how mailing lists work, and how the mail configs work, though, so I really don't have much to help you with here. My experience with email configuration is significantly less than my experience with web development.
Sorry I can't be of more help with this one, but it's a bit out of my domain.