X-Headers are not writing to header of emails. Following error appears in
Oct 3 12:19:06 server.tld /usr/lib64/plesk-9.0/psa-pc-remote: mkstemp(/usr/local/psa/handlers/spool/mlfi.hRHQIU) failed: Permission denied
/usr/local/psa/handlers/spool/ folder has incorrect permissions.
Set correct permissions to folder
/usr/local/psa/handlers/spool/ as follows:
# chmod 770 /usr/local/psa/handlers/spool/
# ls -ld /usr/local/psa/handlers/spool/
drwxrwx--- 2 popuser popuser 4096 Feb 23 10:27 /usr/local/psa/handlers/spool/