VPS Config - Is this enough?

[thanashyam]

HDD:45GB
Guranteed RAM: 512MB

Will this be enough to install and use a Zimbra Server.
Am planning to use this for 10 users which might go upto 20 in the next 6 months. However, Hard disk is not the issue here.

[phoenix]

No, that's way too low on RAM. Check the Requirements in the Quick Start Installation Guide for a Production Server on the Documentation page.