[wishlist] Documentation update for local exim users

[Steltek]

Just an FYI: the ACL you describe in your documentation will apply to all users of the exim server (if the server has clients using it to send out mail, they will have to deal with getting greylisted).

I recommend adding these lines:

  !senders       = :
  !authenticated = *
         domains = +local_domains 

This exempts empty senders (Delivery Status Notifications), authenticated users, and makes the greylisting only take effect for the "local_domains" domains (e.g. the ones you 'receive' mail for).