Actually dependecies are made on package name basis.
I think there should be anothe field that identify the package type.
For instance exim.
Mailman depend on the package exim, but what going on if for any reason I decide to use sendmail?
I broke the dep even if I have an smtp.
I know this is not going to happen very often, just for package like imap servers, smtp servers and in most of the other case the package type is the same of the name (kde, gnome.....).
Proposal to fix it in some way?
I do not want to be polemic, I use exim, but I think the package dependencies system should be a bit more flexible.