What I wanted to do was set up an email address that would pipe to a PHP script. That is, my PHP script would get a copy of the emails. Then the PHP script could parse the file and do whatever; make a database entry or something similar.
I ran into two problems.
First, I would get a return email that said "Local delivery failed." It would have this at the top of the email:
pipe to |/home/accountname/public_html/emailin.php
generated by msg@accountname.com
local delivery failed
I found some website somewhere that suggested changing the file permissions for the PHP script (emailin.php in this case). So that is what I did, and it seemed to help. I used the cPanel File Manager to change the permissions to 754.
That fixed this problem.
The second problem was that despite receiving the email at the script and doing the appropriate things with it, I would still get an error email back. So, even though it all worked, my email would bounce back saying:
A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:
pipe to |/home/accountname/public_html/emailin.php
generated by msg@accountname.com
The following text was generated during the delivery attempt:
------ pipe to |/home/accountname/public_html/emailin.php
generated by msg@accountname.com ------
Again, after a few hours of searching I found someone that suggested changing the hash bang at the top of the script file to this: #!/usr/bin/php -q
That dash q made all the difference.
This was my adventure.