Hi Asad,
Please don't misunderstand. When I say I don't see a need for you to build an external email system, I say it only to give you advice. If you want to make one anyway, it does not bother me for you to do that. But you have not yet seen what my Newsletter will have for features, once you see what I build you may regret spending a month of time on an external one or maybe you really will make a better one. but I will be surprised if you make one that is so much better that people will want to use it instead of the one in the core. Still it is your choice whether to work on an external email feature and do not think it will offend me if you do that, so its not a matter of going out of scope. I'm only telling you I don't see a need for it as I believe the improvements I will make to the core newsletter will meet the needs of most people.
Best,
Joe