PHP4: IMAP trouble

I'm currently writing an RPM spec file for PHP 4.0.1pl2 on RedHat 6.2. I have had a lot of trouble with IMAP, this is what I've done ... (without the --with-imap, the RPM spec file compiles and installs great) %build echo Executing %build cd ../php-4.0.1pl2 export SSL_BASE=../openssl-0.9.5a ./configure --with-mysql --with-apxs=/usr/sbin/apxs \ --prefix=/usr \ --with-mck=/usr/src/mck-3.2.0.4-linux \ --without-gd \ --enable-sigchild \ --with-oracle=/usr/dev/u01/app/oracle/product/8.1.6 \ --with-xml \ --with-ldap \ --with-imap \ --with-config-file-path=/etc/httpd/conf \ --enable-debug=no \ --enable-track-vars \ --with-exec-dir=/usr/bin \ --enable-versioning \ --enable-inline-optimization \ --with-gettext=/usr/share/gettext \ --with-ftp \ --with-modcharset \ --enable-trans-sid \ --with-zlib \ --with-pgsql=/usr/include/pgsql \ --with-ttf=/usr make With the --with-imap directive included, an error appears at "Configuring Extensions" during "checking for IMAP support ... yes" (in %build section). The error reads: "configure: error: Cannot find rfc822.h. Please check your IMAP installation." So, I did a search on the machine for rfc822.h and there was no record of it. I also did a search to see if IMAP was installed, but nothing come up. Believing that IMAP was not installed, I found an rpm at http://www.userfriendly.net/linux/RPM/imap.html and installed it with the command rpm -ivh /usr/src/redhat/RPMS/i386/imap-4.7-5.rpm. Yet, it came up with the message: "package imap-4.7-5 already installed". I am lost right now ... any suggestions are welcome. Thanks for your time, Adelaide