How to customized RSS to email based on the readers' choice?

Hi,

I have a finance aggregator site https://thefinance.sg and I’m looking at improving my feed email delivery by allowing readers to choose what articles they want to receive in their email. It can be based on one or more selected categories and/or the authors.

I know that RSS is able to show feeds based on categories/authors but how do I bring this feature over to email? The reader choose the categories/authors that they want and they will receive just one email with their chosen articles.

Will appreciate if anyone can point me to the right direction.

Thanks.