How can I disable "add application for mailto links" bar in Firefox?
Solution 1:
have you tried going to about:config
There are some keys in there relating to mailto:
network.protocol-handler.external.mailto;true
network.protocol-handler.expose.mailto;false
network.protocol-handler.warn-external.mailto;false
You could try toggling them, I can't test as I can't recreate whats happening for you, I think maybe the first of the three to false maybe a good start,
Be careful when editing this config as it may cause strange things to happen maybe even break firefox.