El Capitan Mail: How to cancel processes in Activity window? I've found a number of questions about the "floating" behavior of the Mail Activity window in El Capitan.  I have a different question:  In all previous versions of Mail.app, processes in the Activity window could be cancelled by clicking on the "Stop" button.  In El Capitan, the Stop button no longer seems to exist.  So the Activity window tells me if something is stuck, but doesn't give me any way to cancel a process.  Is there any way to get that functionality back?

Edited: Here's an example of what I'm talking about.  This window has been stuck on "Connecting..." for more than 20 minutes.  There's no way to stop it and there's no way to find out what's going on.  Turning off Wi-Fi and restarting the app (even rebooting!) didn't do anything; that "Connecting..." process is just still there.
To cancel the activity without the (X) button that is gone since El Capitan, on Mail versions with the V4 format, it seems to be enough to stop the app, go to cd ~/Library/Mail/ and remove the three ExternalUpdates.* files. 

These seem to be the files that keep the queue of remote operations.