One for all you Thunderbird email users out there…(I know there’s some of you out there, I can hear you breathing) Here’s a great little add-on https://nic-nac-project.org/~kaosmos/morecols-en.html which allows you to customise your address book hugely! I’ve used it to create my own labels for the four custom fields, but it also lets you copy a whole address from the context menu, add categories to your contacts so that I can now have a business address book, with different categories of people stored. It’s brilliant!
