From: Jeremy Harris via Exim-users <exim-users@???>
Date: Wed, 3 Jun 2020 18:15:25 +0100
> == marie@localhost R=local_user T=mail_spool defer (-6): mailbox
> /var/mail/ has wrong uid (0 != 1000)
That looks like it thinks the *mailbox* (as opposed to the
directory it lives in), is called "/var/mail/".
I got this this same error very recently. My local_delivery transport
says to put the mail in /var/mail/$local_part_data. In my case the
problem was that in an effort to work around tainted data problems I had
reverted to an earlier version of exim where check_local_user didn't set
$local_part_data, so it thought the mailbox was just "/var/mail/".
Perhaps you have some similar problem.
Ken