'Function for sending new mail.  Also useful for sending notifications from objects or systems.
Args:
recipients (list): list of Player or character objects to receive the newly created mails.
subject (str): The header or subject of the message to be delivered.
message (str): The body of the message being sent.
caller (obj): The object (or Player or Character) that is sending the message.'

def send_mail(self, recipients, subject, message, caller):

    for recipient in recipients:
        recipient.msg(('You    have    received    a    new    @mail    from    %s' % caller))
        new_message = create.create_message(self.caller, message, receivers=recipient, header=subject)
        new_message.tags.add('U', category='mail')
    if recipients:
        caller.msg('You    sent    your    message.')
        return
    else:
        caller.msg('No    valid    players    found.        Cannot    send    message.')
        return
