Know-How Exchange : E-Marketing

I have clients wanting to send out their own email newsletters to their opt-in clients once my company sets up an e-mail template for them. I would like to purchase e-mail newsletter software that would allow me to setup accounts for different customers, let them manage their own e-mail lists, choose pre-made templates, insert their own photo and text, send their own e-mail, view their own statistics, etc...


I would like to purchase a robust program, but I would like to private label it and resell the service to my clients. Does anyone know of any cgi-perl style programs that will do this and do it well. There are a lot of programs out there, but I'm looking for the golden egg.


My clients do not send tens of thousands of e-mails. They send to OPT-IN only where their customers have signed up through their website.