Hi Ravindra,
In regards to the cloud services that are two cloud services:
--Azure - this will give you capabilities to run aspx pages and have a sql server database. You could design an commerce web site/ portal and run it there -- in fact, it is designed for these types of applications that need to be up 24x7.
--Crm Online. You can fully interfact with the web services for crm. In the existing version you can not deploy 'plugins' but with the next version crm 2011 you will be able to deploy plugins.
As for generating emails to users, this one i'm not sure if azure has restrictions on this.
thx,
Alex Fagundes -
www.PowerObjects.com