Date: 2022sep13 Product: Postfix Q. Postfix: postfix/postdrop warning: mail_queue_enter: create file maildrop/N.N Permission denied A. This happened to me when I limited the used systemd to limit Apache to NoNewPrivileges=yes Everything worked ok until a Cubemail (a webmail client) user attempted to send a mail. Cubemail used sendmail which used Postfix maildrop. It needed to setgrp to become user maildrop to do its work. But that wasn't allowed because of the setting. So you cannot lockdown your webserver with that setting if Cubemail is in use. Look for that that settings in:

/etc/systemd/system/httpd.service.d/override.conf /etc/systemd/system/multi-user.target.wants/httpd.service

Once its change to NoNewPrivileges=no do:

systemctl daemon-reload systemctl restart httpd

And:

killall postdrop