Third worst if you have used Lotus Notes mail. I still don't understand how an email and calendar client can slow down a computer like that (going by memory, the last time I used it was at work in 2013 so pre-SSD days).
Everyone at IBM when I worked where used Fetchnotes (internal tool that leaked onto the internet that wraps Lotus notes .so file and allows you to use normal email / contact / calendaring programs and formats).
