razor:

<form action="" method="post">
 <input type="submit" value="Save" name="action:Save" />
 <input type="submit" value="Send" name="action:Send" />
</form>

and controller:

    [HttpPost]
    [MultipleButton(Name = "action", Argument = "Send")]
    public ActionResult Send(MessageModel mm) { ... }

    [HttpPost]
    [MultipleButton(Name = "action", Argument = "Save")]
    public ActionResult Save(MessageModel mm) { ... }