Solidly on Linux Mint now but back in the day when wrangling MacOS I used Hammerspoon to fix these sort of issues - should be doable to monitor and enforce the

Solidly on Linux Mint now but back in the day when wrangling MacOS I used Hammerspoon to fix these sort of issues - should be doable to monitor and enforce the background status of Mail.app and then pause the monitoring when invoked by user (easiest thing would likely be to set hotkey that then also pauses monitoring), and finally resume monitoring when Mail.app goes to background (i.e. user done with active interaction).