FuseMail isn't the same type of webmail client as those included with DA, in the sense that it allows people to read mail sent to any email address.
What FuseMail does is log into your email accounts for you, and download the email into it's own space so you can read it and respond to it through FuseMail.
DWmail appears to do something similar, but I can't tell from the DWmail home page if it's licensed for individual users, or websites, or a server wide solution, so I can't comment on it.
Why isn't atMail in the running?
Jeff