Inbound or Outbound - most people only use one of them.
Fax providers use 'leased lines' - just like cell phone providers. The pricing behind leased lines is that it's more expensive to send 'outgoing' faxes than to receive 'incoming' faxes.
So, you will see web fax plans available with differing usage limits.
Today, most users are just 'receiving' faxes. i.e.; a signed contract, or an order from a distributor.
Outbound faxes have largely been replaced with e-mail blasts.
