[CentOS] postmap: fatal: open database /etc/postfix/sasl_passwd.db: Permission denied

I'm trying to configure mail forwarding through Gmail
on CentOS 6 with postfix, following the blog
http://carlton.oriley.net/blog/?p=31
and I think the blog has missed the step:

# postmap /etc/postfix/sasl_passwd

 - as I've seen in the /var/log/maillog:

postfix/smtp[1926]: fatal: open database /etc/postfix/sasl_passwd.db:
No such file or directory
postfix/master[1831]: warning: process /usr/libexec/postfix/smtp pid
1926 exit status 1
postfix/master[1831]: warning: /usr/libexec/postfix/smtp: bad command
startup -- throttling

But when I try to run postmap, I get

postmap: fatal: open database /etc/postfix/sasl_passwd.db: Permission denied

even though the postfix service is stopped,
the SELinux is permissive and the file is writable:

[root at preferans postfix]# ll
-rw-r--r--. 1 root    root  20K Jun 25 14:50 access
-rw-r--r--. 1 root    root  12K Jun 25 14:50 canonical
-rw-r--r--. 1 root    root 9.7K Jun 25 14:50 generic
-rw-r--r--. 1 root    root  18K Jun 25 14:50 header_checks
-rw-r--r--. 1 root    root  27K Oct  4 20:24 main.cf
-rw-r--r--. 1 root    root  27K Oct  4 20:23 main.cf.OLD
-rw-r--r--. 1 root    root 5.0K Jun 25 14:50 master.cf
-rw-r--r--. 1 root    root 6.7K Jun 25 14:50 relocated
-rw-r--r--. 1 postfix root  113 Oct  4 20:25 sasl_passwd
-rw-r--r--. 1 root    root  13K Jun 25 14:50 transport
-rw-r--r--. 1 root    root  13K Jun 25 14:50 virtual

Has anybody fought this problem already?

Thank you
Alex