postfix local delivery mbox Permission denied

Question

I recently switched from sendmail to postfix.
My /etc/aliases says:

[...]
postmaster: /var/spool/mail/postmaster
[...]

The permissions are:

-rw-rw---- 1 postfix mail 4.9M Aug  9 13:54 /var/spool/mail/postmaster

before it was g=r, I changed it to g=rw for testing.

The error I get is:

[...] postfix/local[4554]: 2D4EF8C1626: to=<postmaster@DOMAIN>, [...] status=bounced (cannot append message to file /var/spool/mail/postmaster: cannot open file: Permission denied)

I don't have a unix user postmaster, if that's relevant.

How can I fix this?

Answer 1

The solution to this, without creating a new user, is to set in main.cf the parameter default_privs = mail.

Keep in mind that it is discouraged to use root or postfix for default_privs.