Welcome to the Community! That certainly sounds like an odd issue. Have you tried this with different browsers and gotten the same issue? It sounds as though maybe there is some add-on's interfering with the download.
Otherwise, it could possibly be your anti-virus messing with the download as well. You may want to check the settings there too.
Hope that helps.
I have the same problem. Using the same browser I can dounload the actual file (not the .php deal) with differnet email providers. Is there a known issue and or fix to this? It's very frustrating!
This is a Chrome issue for me, but it only affects email coming from certain people. If they send me a PDF and I download it, it won't open. But if I download the PHP file, and change the name of the downloaded file TO the PDF name (with extension) it magically becomes the PDF and will open with Acrobat.
The glitch that drives me nuts is anytime I craft an email, the window to attach a file, automatically pops up and I have to manually close it. God forbid I actually want to attach something, because when it auto-pops, it won't actually let me attach anything. So dumb...