Here's a bit of a strange one. One of our osTicket installs seems to have stopped fetching e-mails some time this morning and I don't seem to be able to get it going again. The real headscratcher here is that we have several osTicket installs on this same server, configured the same way, and those are fetching correctly.
Windows scheduled task is configured, running XXXXX\php.exe XXXXX\api\cron.php. Job runs successfully. No errors printed in my PHP error log.
Mailbox is on Exchange 2016 (on-prem). I'm able to connect POP over 995 via client and read the contents of the mailbox, so mailbox looks to be configured correctly and functional. I've reset and re-entered the username/pw in the osTicket email config, which tests and saves those credentials with no issue. Sending a test e-mail from osTicket using those same credentials goes fine.
I've rebooted the server osTicket is running on. I've rebooted the mail servers it's polling against. I've deleted and re-created the cron job. I've deleted and re-created the e-mail address in osTicket. I'm not seeing any activity in the POP logs on the mail server when I run the scheduled task
What am I failing to check, and how stupid am I going to feel for having missed it?
Dashboard -> Information
Emails -> Settings
Emails -> (Address to fetch) -> Remote Mailbox
