Is it mandatory to put the Exchanger server in active directory ?

Yes. You can't have Exchange without AD - except for the Edge role. But a standalone Edge server is close to useless. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.

You need Active Directory for Exchange to work. A good 80% of Exchange is Active Directory related.

Resources: Exchange 2010 System Requirements Why you need Active Directory for Exchange Server 2007Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.