We have mainly two paths:
- create an appliance-like solution based on open source products and develop the glue to connect them together
- build a new mailing list server from scratch
I'm not really in the favour of the second: as I've followed the development of Sympa, to tweak such product for every use takes years.
To determine what path is best, and what solution to use as the core, we should compare the features of the leading existing products, including: