What storage system should I use , If i\'m going to deploy a outlook plugin with VSTO ?
Is it possible to use outlook\'s , which is for email ?
UPDAT
There are numerous options for you to consider, below I've listed all the ones I've seen used in the past.
For Outlook-managed storage you could look into using StorageItem which is a hidden item inside a given folder (Inbox, etc.). Using the StorageItem
you can add custom user properties and file attachments.
You can also create new Folder and mark it as hidden using the PR_ATTR_HIDDEN flag. Adding any mail items or journal items would only be visible to your add-in since you can access hidden folders via the API - but not via Outlook interface.
I've also seen users store information inside Outlook journal items serialized as XML (as is done by jello-dashboard).
You could create a custom store via AddStore to construct a local PST.
Alternately, you could store data external to the Outlook system for consumption by your addin. External stores could be local Environment paths, local/remote databases, or web service calls.