Recomendations for this scenario

Hello,

I am thinking about this scenario:

Server 1: Web Hosting
Server 2: Mail Server Only
Server 3: NS1
Server 4: NS2

In the future I plan to add other web servers.

Do you recommend this scenario?
How would be the best way to achieve it?

Do I need DNS services on server1?
Do I need email services on server1?

Thank you,