Our OSTicket installation has stopped sending emails recently and I am at a loss as to why. We didn't change any of the settings. We have verified the credentials being used are good, and that the email settings are valid. Running on RHEL 7.4. I have updated PHP, but php --version says PHP 5.6 is running while OSTicket says it is using 5.4. Not sure what is going on there. The system logs say: Unable to email via php mail function:nesretep@chem.byu.edu mail() returned failure. In /var/log/maillog, the error that appears is: Feb 27 11 osticket postfix/sendmail: fatal: open /etc/postfix/main.cf: Permission denied". I checked the permissions on that file and apache has read permissions on that file. I tried giving apache full permissions but it had no effect so I changed them back.Attached are some screenshots of important info.