I used to use exchange server for all of the organisations which I administer.
I found Exchange a nice product, but in fact, more suitable for medium to large businesses.
For about 20 users only, exchange is costly and not stable enough because many of them are using it on desktop computers having Windows 2008 R2 server and with a not genuine license.
What are alternatives available for those small businesses? Any free or open source solutions?
Hosted email is not a good solution because:
1. They need one time payment.
2. Many branches are connected to the HO only and don't have access to the internet.