Question : do i need licenses per user if i buy exchange server?

So I have been asked to price up a mail server. Do i need to buy access licenses for each user when i price it up?

Cost of physical server
+
Server OS (server 2008)
+
Exchange license
+
Access License x #users

= cost

Answer : do i need licenses per user if i buy exchange server?

Yes, a CAL is required per user but you can also do it per device if you have more users than devices (computers).
The Small business server (SBS) includes the Exchange server and the SBS CAL covers several MS products (Limited for small business).

http://www.microsoft.com/exchange/2010/en/us/exchange-2007-how-to-buy.aspx
http://en.wikipedia.org/wiki/Microsoft_Exchange_Server

How many users are you looking at now ? and in the future ??
How many messages per day per user ?
Size (KB) per email ?
Volume licensing, MLP, open  ?

Look at Exchange hosted email by other service companies.
Does it have to be MS Exchange ? Look at other solutions eg. self hosted on Linux or Goggle Mail or several others.