Adding the “send to” via email action to your Nemo/Ubuntu
Saturday 4 November 2017 at 18:30
How to get a “right click, send by email” menu in Nemo file browser:
Create the file:
.local/share/nemo/actions/thunderbird.nemo_action
Just cut and paste this inside that file and you’re done 
[Nemo Action] Name=Send by Email Comment=Send by Email the files Exec=thunderbird -compose to=,"attachment='%U'" Icon-Name=thunderbird Selection=notnone Extensions=nodirs; Separator=, EscapeSpaces=false
Source: http://www.dotmana.com/weblog/2017/11/adding-the-send-to-via-email-action-to-your-nemoubuntu/