I am developing my first add-in for the Outlook Web App. It's not clear to me where I should store larger pieces of data provided by the user (e.g., big chunks of text, images) and to be associated with the add-in (as opposed to belonging to a particular mail item).
My impression is that RoamingSettings is supposed to be for relatively small stuff, and therefore not a good fit. I could store the data on OneDrive, but I prefer not to expose the data to the user outside of the add-in UI. I found <a href="https://stackoverflow.com/questions/10171454/what-storage-should-i-use-for-a-outlook-plugin" rel="nofollow">this SO entry</a> but the answer seems to be more applicable to desktop Outlook, not OWA. I suppose I could store the data on my own server if I need to, but I first I want to know if there's already something in the OWA architecture that would serve this purpose.Answer1:
RoamingSettings is the default choice for storing application/user settings/data, but there is a 32K limit that can be used per setting and 2MB total for all settings used by your add-in. An alternative approach is to use EWS to create a message in a hidden folder and store your data in the message body.
<a href="https://blogs.msdn.microsoft.com/mvpawardprogram/2016/01/26/unifying-your-web-dev-skills-for-office-add-ins/" rel="nofollow">https://blogs.msdn.microsoft.com/mvpawardprogram/2016/01/26/unifying-your-web-dev-skills-for-office-add-ins/</a>Answer2:
I am a developer for Microsoft working on Outlook addins.
You should store the larger data with your service / on your server as you noted. A message is generally not suited for storing random data for your addin. Using makeEwsRequestAsync requires a ReadWriteMailbox for addin permission that may not be necessary otherwise.
Another note is that the 32K limit is the limit for RoamingSettings per addin for Outlook. It's not 2MB.