While emacs doesn't have this feature, you can evaluate elisp on startup:
emacs --eval "(setq fill-column 60)"
This will set the value for the initial buffer, however you may want to apply this to a mode instead, read on....
If you only want this for a spesific mode, you an do:
emacs --eval "(add-hook 'mail-mode-hook (lambda () (setq fill-column 60)))"
With emacs 27 you can draw this on startup too:
emacs --eval "(add-hook 'mail-mode-hook (lambda () (setq fill-column 60) (display-fill-column-indicator-mode)))"
Although in this case you would typically do this in your init file,
not using the command line, eg:
(add-hook 'mail-mode-hook
(lambda ()
(setq fill-column 60)
(display-fill-column-indicator-mode)))