mail object does not report bad property names

[macMikey]

there is no message returned if a bad property is assigned to a mail object.
example: i was trying to add an attachment to a message, but instead of using the attachments property name, i used attachment. no error was reported, but, obviously, no attachment was included in the email, either.
i think that the object should check for bad property names and return an error if there are any.