Hey,
I compared the two an they are the same, line per line, so I don't know what's the difference. Could be something in permissions but I don't know for sure, just know that it's working now.
Thanks
Yes it must have a different permission setting. The api/pipe.php file needs to be 755 to be executable. If you look at it using FileZilla, it will look like this:

You must have set that permission when you first set up email piping. It is easy to do!
Anyway, now you know for the next time you want to upgrade.
have same experience in centos 7,
change to fileformat to unix to fix the problem:
in vi:
set fileformat=unix
then save.
I just saw your solution now, many months later.
Thank you for posting this! I added the vi instruction to the Troubleshooting page.