Due to some security requirements in a project, I need to disable the attachment download in OWA (with other security requirements acomplished with Access Control). To do that it was very simple and onlye was needed some clicks into the Exchange Online admin center:
First of all, access to the EXO AC, go to permissions, Outlook Web App policies, then you have two options, or create a new policy or to modifiy the default, one. Whatever option you choose, the only change needed is to uncheck the “Direct file Access” checkbox
In case you create a new OWA policy and specify the following:
In case you create a new policy, remember to set the policy to a bunch of pilot users to test it first, before setting the policy to the whole company
But If you want to do it by PowerShell, you can do it by executing the following (remember to connect to EXO by PS):
Get-OwaMailboxPolicy | Set-OwaMailboxPolicy -DirectFileAccessOnPublicComputersEnabled $false -DirectFileAccessOnPrivateComputersEnabled $false
Once this has been done, the user is not able to download the file, but he can edit the file into the Online version of Office, great isn´t it?