Pasting without formatting

For a longer text, I prefer to write it in Word, before pasting it in my email or browser window (Firefox).
Thunderbird is very convenient since it has the standard option "paste without formatting".
Firefox has not.
Then I have two options left with Firefox.
- I paste and remove by hand all formatting artefacts
- I save the Word document as txt and copy this.
Question: did I overlook a more quicker solution?

Thanks, but this add-on intends to remove formatting when copying text from a website and not when pasting into a website window.
I think the easiest solution for me is editing a text not in Word but in Notepad.

Ctrl+Shift+V should work in Firefox:

How to paste as plain text in Firefox without third party plugins

Firefox: Paste as plain text (CTRL + SHIFT + V) is broken/inconsistent [FIXED]

Thanks @NMI for guiding me to this.
It is exactly what I need.