e-mail addresses not saved

I have to re-enter the e-mail addresses everytime I want to send an article from my laptop to Kindle. There is no checkbox visible for remembering the addresses, as is on my Firefox installation on my desktop.
I use Firefox 54 and the latest PushtoKindle addon version. I have registered an exception in the settings to preserve cookies from http://fivefilters.org when closing the browser. I use ublock and Ghostery, both have been disabled when calling up fivefilters.org

Hi there, I’ve just tested this in Firefox 54 and cannot reproduce the problem. I should point out that we use Local Storage, not cookies, to store that information. So if you’ve got local storage disabled, that might be the issue. You can find out a little more about the setting in Firefox here http://kb.mozillazine.org/Dom.storage.enabled and https://stackoverflow.com/a/25050910 (instructions are to disable, but same ones should enable if it’s disabled).