It would be awesome to have an on-attach feature for outlook add-ins much like the on-send feature. When the user tries to attach a file while composing an email, the add-in gets a callback to inspect the attachment (type, size, etc.). Then the add-in should be allowed to open its task pane for related actions.

This is an important feature in terms of user experience for file storage applications (like SureDrop or Dropbox).

For example, consider iPhone. If we want to email a large file:

• The phone's email client detects that the email is too large to attach directly


• It asks me if I want to share via MailDrop


• If i say yes the file is uploaded to MailDrop in the background and a link is sent

Google does the same in gmail:

• You can send up to 25 MB in attachments. If you have more than one attachment, they can't add up to more than 25 MB.


• If your file is greater than 25 MB, Gmail automatically adds a Google Drive link in the email instead of including it as an attachment.

So, file storage platforms will benefit immensely with the introduction of this functionality in outlook add-ins.