I'm operating a Debian11 server with Ispconfig 3.2. DKIM signing is done by amavisd-new-2.11.1 (20181009). I've noticed that locally generated outgoing mail (directly with the php mail() function from the domain's associated website) is not signed by DKIM. It works when it's sent through SMTP (connecting to localhost:25, unauthenticated) and verifies ok so DKIM is set up properly, keys work, etc. The return-path and from headers are OK in both cases (i.e. mail is coming from webmaster@domain as they should). What am I missing to fix this? I recall that there was an earlier one liner patch to amavisd-new to fix some sort of local DKIM signing issue but I'm not sure if it's relevant.