Address extensions not working (firstname.lastname@example.org) was forced closed so I can’t add to that.
I tried a completely clean install and narrowed down what happened.
We changed recipient_delimiter in /etc/postfix/main.cf from + to - (because that’s what was on the old mail server). This worked for earlier versions of mailinabox.
After a recent upgrade it stopped working and even changing back to + for testing did not work.
Changing to both ± (which is valid on the version of postfix mailinabox uses) doesn’t work either.
On the clean install + works but - does not.