In Office 365, Emails can accessed from anywhere (within or outside of the company). Want to block Email attachment download from outside of the company. Emails should be accessible from outside of the company but attachments should be blocked to download from outside of the company. This for protection.
You may be able to do this but the capability, I think, isn't available to every license SKU.
Unfortunately, I can't remember off the top of my head, the right part of the toolset but I think you can do this if you have "Enterprise Mobility & Security" which is an add-on license. You should also be able to do it if you manage your corporate devices via the InTune mobile device manager.