"Private Tab" used to open a new tab (sent from an external application) in the private mode when the currently active tab was in the private mode. But in FF 40 & 41, this is not working anymore. If I click on a link from for instance my Thunderbird, the link is opened in the normal mode, not private mode anymore.
This is expected behavior and was fixed in recent update: #184
You should set extensions.privateTab.allowOpenExternalLinksInPrivateTabs = true in about:config.
"Private Tab" used to open a new tab (sent from an external application) in the private mode when the currently active tab was in the private mode. But in FF 40 & 41, this is not working anymore. If I click on a link from for instance my Thunderbird, the link is opened in the normal mode, not private mode anymore.