Thunderbird does still have a thing to customise the from address. Most other mail clients have something, but it’s a bit ad-hoc. In Apple Mail, you need to add each address as an identity: I wish you could add a wildcard pattern here for things. It’s very useful with things like postfix’s relay maps, because my mail server can authenticate clients and then can forward via the correct authenticated relay, so I don’t need to add credentials for my FreeBSD.org address (for example) to every client device to be able to use it, I just set that as my from address, postfix sees that I am allowed to send from that address and sends it to the FreeBSD mail relay, with my username and password.
Yes, I remember Thunderbird let me edit the whole From: address as a free-text field, where in later versions it would only have pre-set “Identities” I could pick from.
It’s still possible. In the drop down list, one option is ‘edit From address’. This lets you edit the field as a free form text box.
oooh neat, didn’t notice that!
A fairly recent addition to my stack is netdata – I know it looks way over the top, but it’s really easy on resources and makes debugging issues / reading up on system events so much easier.