Rmail, movemail and maildir

[Mike Gran]

Hello.  This is my first time ever asking for help on emacs, but,
this one has me stumped.

(This is GNU Emacs 25.1.1 (x86_64-redhat-linux-gnu))

I'm trying to set up old-school rmail, and I want it to fetch
mail from a Maildir directory on my home filesystem.  According to
the instructions, I need to install movemail, which I did, and
then set some variables.  So my .emacs now has

;; MAIL
(setq rmail-movemail-program "/usr/local/bin/movemail")
(setq rmail-primary-inbox-list '("maildir:///home/mike/Maildir"))
(setq rmail-movemail-flags (list "-p --emacs"))

But I can't get emacs rmail to invoke movemail.

I can run movemail manually like so, which works.

movemail -p --emacs maildir:///home/mike/Maildir ~/RMAIL --verbose

The docs here are actually a bit unclear.  They discuss how to make
a URL for a mailbox for movemail, but they don't tell you where
that URL should go.

https://www.gnu.org/software/emacs/manual/html_node/emacs/Movemail.html

Thanks in advance,

Mike Gran