I know this is an old post, but I found it and then found someone who suggested Total Mail Converter. I was able to convert my folder with 2k .msg files into .txt. It also allows you to convert into PDF and other popular formats.
It's a great tool that I am glad someone suggested as it will save me several days.
FYI - My project is combining the .msg files into one text file so that I can run a script to extract certain information from the files (ie: email and links). Instead of 2k files, I can work with one.