we are currently developing addins for email clients, one for Outlook, one for Thunderbird, to be able to encrypt and decrypt emails based on attribute-based encryption.
As our goal is to encrypt in-transit, one requirement is to store once decrypted emails locally on the file system, such that it is possible to search in decrypted mails within the mail client.
I already found several other addins that create outlook data files (PST) to store data. However, it seems this functionality is not available if one writes an addin based on Node (https://learn.microsoft.com/en-us/office/dev/add-ins/quickstarts/outlook-quickstart?tabs=yeomangenerator). If one writes an addin via VSTO (https://learn.microsoft.com/en-us/visualstudio/vsto/walkthrough-creating-your-first-vsto-add-in-for-outlook?view=vs-2019) it seems to be possible.
So my question is if anyone knows if it is possible to realize this via a Node addin, and if so, how to implement it? Or are there other alternatives?
Outlook web add-ins (can be Node based ones) work in the context of a mail or appointment item and don't have any direct access to the Outlook store. The web add-in can be activated and deal with the currently selected item in Outlook or use EWS or Graph API for retrieving other data.
Add-ins that allow creating additional stores in Outlook profiles are COM based ones (for example, VSTO) - they have full access to the Outlook object model.