I have the extension "Advanced SMTP Settings" installed on my instance. This extension adds a popout panel to the Mail page with a link to the advanced settings, as can be seen in the screenshot below:
However, I've noticed that in v20.4 (to be precise, 20.4.27797.7403) the popout no longer appears:
It's not just the "Advanced SMTP Settings" extension that's affected by this bug, but other extensions that add the popout panel too, like "Download Audit Log as CSV".
Customer support service by UserEcho