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).

Well... I don't know exactly what the OP meant by "technology", but Notes at least wasn't supposed to be a development platform.

It surely was a development platform, but wasn't supposed to be one.

I should have been more specific here indeed. I meant more library or framework, not technology in the broader sense. My apologies.

You just reminded me of the nightmare Lotus Notes was.