Could someone help me to identify the standard requirements needed for a mass mailing application. The application is done in ASP.NET C#
Depends how you define "mass mailing". Seriously. Can e anything from a quad processor server to my handy.
50.000 emails once per week? my handy can handle that. Especially if they can take a day or two to be delivered.
5.000.000 emails every day - needs a server. Especially if they should be delivered within an hour or so.
WAY too little information about what you want to do. For example, will the server do the spooling, or not? Most providers want them to use their own servers for actual delivery, so you would basically just talk to one email server.
It all depends, and you are really givine zero relevant information.