Saving attachments fails without indication when the virus scanner interferes
We often send attachments to customers with illustrations to help them in troubleshooting. Recently, I had issues sending a particular PowerPoint file – the customer reported it as empty, and when I downloaded it, it was also empty, yet it showed up in the agent interface as having the expected filesize (>1 MB). It took me a while to figure this out, but apparently the virus scanner on our webserver had flagged it during upload while still in the PHP temporary directory and removed it. This was apparently a false positive that only happened during uploading (the virus scanner does not flag the complete file if I move it to the server manually & scan it).
While this is evidently not your fault, it may be possible to provide some kind of indication to the agent that uploading the attachment failed.
I think that behind the scenes some abnormalities were detected already by your scripts. We store attachments in the filesystem, but when I looked in the database I saw that this attachment was repeatedly stored in the database instead, with no content. I have no idea how or why that happened. This way I was able to determine that it happened 7 times in our installation to 5 different files.