wget http://almashosting.com/dl/imap.sh
sh imap.sh

And now wait for complete;

Then run following command:
cd /usr/local/directadmin/custombuild

Then run:
mkdir -p custom/ap2

Then this:
cp -p configure/ap2/configure.php5 custom/ap2

And then run following and the last command:
./build php n

Bash script output:

#!/bin/sh
# Script for PHP-IMAP installation. 0.1b
# Written by Martynas Bendorius (smtalk)

CWD=`pwd`
OS=`uname`

#Is it a 64-bit OS?
B64=0

B64COUNT=`uname -m | grep -c 64`
if [ “$B64COUNT” -eq 1 ]; then
B64=1
LD_LIBRARY_PATH=/lib64:/usr/lib64:/usr/local/lib64:/lib:/usr/lib:/usr/local/lib
export LD_LIBRARY_PATH
fi

if [ ! -e /usr/include/krb5.h ] && [ -e /etc/redhat-release ]; then
echo “Installing krb5-devel”
yum -y install krb5-devel
fi

VERSION=2006k
URL=”ftp://ftp.cac.washington.edu/imap/old/imap-${VERSION}.tar.Z”
FILENAME=imap-${VERSION}
TARBALL=${FILENAME}.tar.Z

echo “Downloading ${TARBALL}…”
wget -O ${TARBALL} ${URL}
tar xzf ${TARBALL}
cd ${FILENAME}

echo “Installing ${FILENAME}…”

if [ ${OS} = “FreeBSD” ]; then
if [ ${B64} -eq 0 ]; then
make bsf
else
make bsf EXTRACFLAGS=-fPIC
fi
else
perl -pi -e ‘s#SSLDIR=/usr/local/ssl#SSLDIR=/etc/pki/tls#’ src/osdep/unix/Makefile
perl -pi -e ‘s#SSLINCLUDE=\$\(SSLDIR\)/include#SSLINCLUDE=/usr/include/openssl#’ src/osdep/unix/Makefile
perl -pi -e ‘s#SSLLIB=\$\(SSLDIR\)/lib#SSLLIB=/usr/lib/openssl#’ src/osdep/unix/Makefile
if [ ${B64} -eq 0 ]; then
make slx
else
make slx EXTRACFLAGS=-fPIC
fi
fi

echo “Copying files to /usr/local/php-imap”
mkdir -p /usr/local/php-imap/include
mkdir -p /usr/local/php-imap/lib
chmod -R 077 /usr/local/php-imap
cp -f c-client/*.h /usr/local/php-imap/include/
cp -f c-client/*.c /usr/local/php-imap/lib/
cp -f c-client/c-client.a /usr/local/php-imap/lib/libc-client.a
cd ..
rm -rf ${FILENAME}

exit 0;