I would like to know this too. Currently I use Thunderbird and just grab all the eml files. There is an addon I use that exports an html file containing a table

I would like to know this too. Currently I use Thunderbird and just grab all the eml files. There is an addon I use that exports an html file containing a table of everything and it's index. Then I zip it up with the most recent date as the name and put it in a folder. What I want is to just export my email box and be able to access it like an archive as if I was opening a SQLite database.