Mailto links not working

Summary:

I am trying to embed a mailto: action link in a report to create an email to a requester where they need to take action, for example where they have an invoice on a GINR report.

When I click the relevant column, a new tab opens however nothing opens in the email program (Outlook).

On checking the URL on the new tab, the link opens as mailto/ instead of mailto: When I replace the / with : manually in the address bar, it opens the email as expected but the URL also reverts to / from :.

Has anyone ever come across this and know how to fix it? Part of the complication is that the email address is tokenised rather than fixed because it depends on the line on who needs to be contacted. The URL I am using in the link is