Wrote a small Outlook 2016 plugin (VSTO) that will easily send all attachments in an email to your Calibre database. All code and the installer can be found here: https://github.com/timdams/SendToCalibre_OutlookPluginVSTO
See here how it works in full action:
A future blog post will explain some of the inner workings.
Tim Dams 
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