Running Mojave on cMP 4,1=>5,1 and for the most part it's working well. I have the audio stutter problem, but that should be fixed with the install of some later CPUs. But... Maill.app slows down. E.g. if I start it in the morning it runs fine at good speed. Selecting a different message displays it almost instantaneously. Then after 1 or 2 days (sleeps over night) I notice it is slow and eventually just selecting e.g. the next message in the list can take 10 seconds or so to display the message content. When simply trying to quickly flick though messages to see what to keep or trash etc, the slowness becomes intolerable and I have to Quit the app, then re-start it. After which it runs at full speed for another day or so. Just to be clear, I doubt it runs at full speed then suddenly slows right down. I suspect it gradually slows down after it starts, until it becomes noticeable and then unacceptable and I have to re-start the app. Anyone else experiencing this and/or any idea of the cause and how to eliminate the problem?