Can I selectively disable the "This location may be unsafe" warning in Outlook for certain protocols?

I have developed a custom protocol handler (let's call it "foo://") for use on my system by registering an executable at HKEY_CLASSES_ROOTfooshellopencommand. So far, so good.

I would like to send and receive links that use the foo:// protocol in emails. However, when I try to open one of these links in Outlook, I get the "This location may be unsafe" message below. I could just click "Yes" every time, but I would rather stop the message from appearing in the first place.

I've found instructions for how to disable the waing altogether (e.g. here - Add a DWORD value "DisableHyperlinkWaing" = 1 to HKEY_CURRENT_USERSoftwarePoliciesMicrosoftOffice...Common), but that's not what I'm after. Rather, I'd like to disable the waing on a per-protocol basis, so that my "foo://" protocol is whitelisted, but other protocols still show this waing when appropriate.

Can I do that? I'm using Outlook 2013.