Ubuntu 18.04 fresh installation, Thunderbird inbox "invaded" by large icons (coloured emojis)

This fixed it for me:

sudo apt-get install fonts-symbola

but turns the icons b/w!

From https://ubuntu-mate.community/t/thunderbird-with-huge-icons-emoticons-mate-18-04/16249/23

Here's a way of getting colored icons:

sudo apt-add-repository ppa:eosrei/fonts
sudo apt-get update
sudo apt-get install fonts-twemoji-svginot

I did not have to uninstall fonts-symbola for this to work but I don't know how Thunderbird decides which to use.

New font info from http://www.omgubuntu.co.uk/2016/08/enable-color-emoji-linux-google-chrome-noto

While not a long-term solution (but should work until the fix for the bug is deployed), you can install the EditEmailSubject add-on for Thunderbird. It will allow you to delete offending characters from message subjects.

I find the add-on useful generally so this works for me.