I want to maintain a list of domain names that provide web-mail services.I searched and received a list of 1634 domains(Free Public web-mail services)However, is it possible to get updates, if any new domain registers to offer web-mail service,through scripts or through tools.Or, is it possible to tell by looking at domain name in the http header (through scripts/tools), whether it is offering web-mail service?
List of Domains offering Web-mail services
web services;networking;web api;http request
To answer your second question - no, it isn't feasible to automatically scan for webmail providers.A web mail provider is simply a web application. It doesn't follow any specific standard or expose a specific interface. It's just a web site with functionality.It can be mostly server-side or have client-side elements.It can be written in PHP, or ASP.NET, or in native C++ via a CGI gateway.It can be hosted, like Gmail or Yahoo mail, or it might be a software package that's installed on thousands of different servers - you can install SquirrelMail on your own cheap $5/mo PHP hosting.It can supply web-based services for the general public, or to a specific group (universities, organizations, customers) or can be a private server.So no, any hope to get a definitive list of all webmail service providers automatically is doomed to failure.