Though it appears to have been last updated on 2010-09-18, this class seems a bit dated. It is full of undefined variables that throw PHP warnings and uses some functions that are deprecated in PHP 5.3, so it took me quite a while to get working under PHP 5.3.3. I used this class as a starting point, converted it to a Kohana library and fixed the bare minimum that I needed to get it working to parse some IMAP messages retrieved from a remote server. Definitely not a simple plug-and-play script, but it saved me some time of having to write parsers for the various bounce email formats that are out there. I suspect it is in need of more updating to recognize newer MTAs and for better compatibility with newer versions of PHP. So, with all that said, I did find the class useful once I spent an hour or two beating on it with my preferred IDE/debugger.