Oh, it always annoyed me, that you can't simply drag-and-drop attachments into the writing window in Mozilla Thunderbird as you can in Outlook.
Especially if it's a couple more, it's pretty tiring to always click "add" and select each file.

Now, completely by accident, I found out, you can drag-and-drop files, even multiple ones, onto the "attachment" button (and into the subject field) in Thunderbird!
That is months after my first use and I don't consider myself a computer noob.
Now, let's talk about ease of use, again.