You should install PHP Mailparse extension with pecl.
You can use this guide http://help.directadmin.com/item.php?id=400 it describes how to install APC extension; commands in the step (1) are almost the same if you install Mailparse.
Thought I'd resurrect this thread. I just searched up mailparse as it's a recommended (not important) module for Blesta. I followed @zEitEr 's link above and I really want to thank him for an amazing script! It has saved me so much time messing about with custom configure.phpXX files and building it all that way. It was quick and it's a must have tool I think for PHP module installations for multiple PHP installs.