I just upgraded from Mavericks to Sierra. Everything was working fine in Mavericks and most things are working ok in Sierra, but the very first time I tried to reply to a message in Mail it went crazy. Whenever Mail is active the message I tried to send is jumping on the screen alternating with the Mail window a couple times a second. I can do nothing with it except quit Mail.
I hope someone can help!
I am working on a 15" mid 2012 MacBook Pro.
See if it is the same in the Safe Mode.
Safe Mode - About El Capitan
also Sierra
Safe Mode Startup – El Capitan. also Sierra
If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor. Please use copy and paste as screen shots can be hard to read. On the screen with Options, please open Options and check the bottom 2 boxes before running. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown.
Mail has gone spastic
