Q: Two days ago I updated to El Capitan. Mail previously had several folders in which I had stored emailed newsletters, and on line tutorials. They are now gone. Is there anyway to recover these lost emails?

Thanks Leroy.

Just before receiving your reply, and after following other suggestions to rebuild mail. I discovered that the folders were there. I just needed to click on Show, next to On My Mac, rather than on the Plus icon.

Now I just need to figure out how to restore the Notes folder. Which I find convenient  to send content from my iPad to Mail on the Macbook, to easily continue where I left off on the iPad.

Thanks again for the help.

David