Bug#4477: Emacs doesn't use /etc/mailname

[Ian Jackson <ian@chiark.chu.cam.ac.uk>]

Package: emacs
Version: 19.31-2

-chiark:~> grep mailname /var/lib/dpkg/info/emacs.*
-chiark:~> cat /etc/mailname
chiark.greenend.org.uk
-chiark:~> hostname -f
chiark.chu.cam.ac.uk
-chiark:~> 

But, after C-h C-v mail-host-address RET:

-----Emacs: *scratch*      12:40am 0.34 Mail   (Lisp Interaction)--L1--All----
mail-host-address's value is nil

Documentation:
*Name of this machine, for purposes of naming users.
-----Emacs: *Help*         12:40am 0.34 Mail   (Help View)--L1--All-----------

Ian.