Our OSTicket installation has been running like a top for several years. I have done relatively regular updates to the software. We are running it on a Hostgator shared server configuration (not ideal, but cheap). About 3 weeks ago, it suddenly stopped sending emails (except for the admin new ticket creation messages - those are still being delivered, but automated ticket responses, and agent replies are not being delivered.)
Here is our software version and server software:
We do have a bit of a unique situation for email delivery (because Hostgator does not allow access to external SMTP servers).
All checks pass and sending messages from the diagnostic tool within osTicket are delivered without issue.
I am stumped and would greatly appreciate any assistance/ideas that people might have.
Thanks,