As title really... I've scoured the other similar threads and whilst I'm getting a similar problem (cron is executing without error but not retrieving from the imap folder(s)) I've tried everything clearly suggested in them, to no avail.
I've tried the task with the username values of nobody, root and www-data set...
* * * * * nobody /usr/bin/php /var/www/html/api/cron.php
/var/log/syslog output (via grep CRON /var/log/syslog):
Mar 24 15:55:01 rewind CRON[1458]: (root) CMD (root /usr/bin/php /var/www/html/api/cron.php)
The imap folder does not get processed in this instance. I've modified the php.ini to output PHP errors to the syslog, but nothing is returned when the log is tailed other than the cron continuing to run.
if I run sudo -i to root or just call the PHP command from the CLI (/usr/bin/php /var/www/html/api/cron.php) then the script executes, as does the OSTicket AutoCron if I access the UI.
The server is Ubuntu 16.04.1 Xenial LTS running PHP 7.0.15 & Apache/2.4.18. Any & all help would be appreciated - if I'm missing a log file record, just ask.