original configure script:
./configure --with-apxs=/etc/httpd/bin/apxs --enable-track-vars --enable-ftp --with-gd=../gd-1.8.4 --prefix=/etc/php --sysconfdir=/etc/php --with-imap=../imapServer

Note: ../imapServer is the dir where I gunzip'd the source files.

This script gives the error:
Cannot find rfc822.h. Please check your IMAP installation.

Then I do another configure where I specify the location of rfc822.h:
./configure --with-apxs=/etc/httpd/bin/apxs --enable-track-vars --enable-ftp --with-gd=../gd-1.8.4 --prefix=/etc/php --sysconfdir=/etc/php --with-imap=../imapServer/src

Now the error is:
Cannot find imap library. Please check your IMAP installation.

I have also downloaded the newest IMAP source from http://www.washington.edu/imap/, but the same error messages appear.

By the way, PHP, Apache, and the IMAP server were, and still are, working fine.  It's just that I cannot recompile PHP with IMAP support.