@MagicMint's (fixed) script to start Thunderbird in background (Cinnamon) (https://community.linuxmint.com/tutorial/view/2222)

thunderbird

#!/bin/bash
# {~,/usr/local}/bin/thunderbird (MagicMint) O1010
# Start thunderbird minimized if desired

mailer="/usr/bin/thunderbird"

help_msg() {
cat <<-EOF
	`awk  'FNR==3 {print gensub("# ", "", 1)}' "$0"`
	Usage: `basename $0` [-min] [URL] | [-h] | [--help]
EOF
}

case $1 in
	-h | --help )
		help_msg
		echo
		read -p "Press [Enter] to continue or [CTRL-C] to abort"
		eval $mailer --help 2>/dev/null
	;;

	-min )
		shift
		eval $mailer "$@" &
		until test $THUNDERWIN; do
			sleep 1
			THUNDERWIN=`xdotool search --name ".*- Mozilla Thunderbird$"|head -n 1`
		done
		xdotool windowfocus --sync $THUNDERWIN
		xdotool key Ctrl+Alt+Super+Down
		;;

	*) exec $mailer "$@"
		;;
esac
#End of script