asp.net mvc 4 - OpenPop.NET save to database or save file -

I am using OpenPop.NET to retrieve emails from clients. I think that is a service that is working on the background, when the customer tries to check it, instead of storing the newly received mail from time to time rather than receiving it, because: Performance:

Here's the question: Is this a better idea to store email information in a database or save it to a file

I was thinking that there would be a better database solution because Message-ID This way I can open email details using my own IDMessage But this is my first time working with receiving emails and I am not sure if there is a purpose that I should not do in this way. That's why I am open for opinions and advice.