Here are some VM customization variables that don't really fit into the other chapters.
nilvalue means to read and write BSD Mail(1) style Status: headers. This makes sense if you plan to use VM to read mail archives created by Mail.
nilvalue means to use a crufty regular expression that does surprisingly well at beautifying UUCP addresses that are substituted for %f and %t as part of summary and attribution formats.
nilvalue should be a list of hook functions to run when a buffer enters vm-mode. These hook functions should generally be used to set key bindings and local variables. Mucking about in the folder buffer is certainly possible, but it is not encouraged.
nilvalue for this variable causes VM to remove empty (zero length) folder files after saving them.
tgives VM free run of the Emacs display; it will commandeer the entire screen for its purposes. A value of
nilrestricts VM's window usage to the window from which it was invoked. VM will not create, delete, or use any other windows, nor will it resize its own window. A value that is neither
nilallows VM to use other windows, but it will not create new ones, or resize or delete the current ones.
vm-yank-message. When each hook function is called, point will be at the beginning of the yanked text and mark at the end. This is not a VM specific variable, but rather an external variable that VM honors so that citation packages such as SUPERCITE can be used with VM.