can't config with imap

Hi, I'm tyring to configure so I can install php with imap support and am getting the following error... error: Cannot find rfc822.h. Please check your c-client installation. this is my ./configure stmt... ./config --with-aspxs2=/usr/local/apache2/bin/apxs --with-mysql=/usr/bin --with-iconv --with-curl=usr/bin --with-ftp --with-imap I've googled 'rfc822.h' and 'c-client installation' among other things, but I'm getting pretty lost as to what this all means. Can someone direct me a bit? Eric some background: - I'm trying to upgrade from php 4.3.9 to 4.3.11 and I decided to simply install 4.3.11 without uninstalling 4.3.9 since I can't find any uninstall docs. Hoping that's not the conflict. The install seems to work without the --with-imap option. - I'm running Linux Fedora Core 2