You may see quite a few maildrop warning messages in the postfix logs such as
postdrop: warning: mail_queue_enter: create file maildrop/xxxx.xxxx: Permission denied
postdrop: warning: mail_queue_enter: create file maildrop/yyyy.yyyy: Permission denied
The error occurs when postfix is not able to write under the “maildrop” folder and hence unable to send emails. This is due to incorrect ownership on the ‘maildrop’ folder i.e. the “maildrop” folder is not owned by ‘postfix’.
Check the ownership/permissions of the postfix files:
# /etc/init.d/postfix check
postfix/postfix-script: warning: not owned by postfix: /var/spool/postfix/public
postfix/postfix-script: warning: not owned by postfix: /var/spool/postfix/maildrop
Solution:
Stop the postfix service:
# /etc/init.d/postfix stop
Kill the postdrop processes:
# killall -9 postdrop
Correct the ownership of the above directories:
# chown postfix.postdrop /var/spool/postfix/public -R
# chown postfix.postdrop /var/spool/postfix/maildrop -R
Now, start the postfix service:
# /etc/init.d/postfix start
Emails should now be working fine.