Is there any way we can configure multiple plesk panels ( i.e 10 plesk vps ) to a single Smarter Mail server ? Is it possible ? or do I need to purchange smartermail for each plesk vps ?
Multiserver solution will be released soon as Parallels Plesk Automation - http://www.parallels.com/products/plesk-automation/
At the moment there is no possibility for using one mailserver for many Plesk servers.
I wouldn't recommend Plesk Expand at the moment because it is being superseded soon by our new mentioned solution. It will allow for the centralized Mail, DNS plus a lot more.