Centos – Help needed on installing imap on CentOS 5

I'm very new when it comes to webservers. I have my own DDS but no imap installed at it. I asked my ISP to install it but they charge a lot. In my opinion it shouldn't be too much work so I started googling and came accross this article: http://www.electrictoolbox.com/install-php-imap-centos/.

It seems like i only have to execute 2 commands:

sudo yum install php-imap
sude /etc/init.d/httpd graceful

I'm logged on as user 'root' to my server, this is the account they provided to me. But when I try the first command I get this output:

[root@dds ~]# sudo yum install php-imap
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * addons: mirror.oxilion.nl
 * base: mirror.oxilion.nl
 * epel: ftp.nluug.nl
 * extras: mirror.oxilion.nl
 * rpmfusion-free-updates: mirror01.th.ifl.net
 * rpmfusion-free-updates-testing: mirror01.th.ifl.net
 * rpmfusion-nonfree-updates: mirror01.th.ifl.net
 * rpmfusion-nonfree-updates-testing: mirror01.th.ifl.net
 * updates: mirror.oxilion.nl
Excluding Packages in global exclude list
Finished
Setting up Install Process
No package php-imap available.
Nothing to do

How can I achieve to install php's imap functions?

I hope to hear from you!

Kind regards from Holland.

Ben Fransen

Update
Output from less /etc/yum.conf (first about 20 empty lines)

[main]
cachedir=/var/cache/yum
keepcache=0
debuglevel=2
logfile=/var/log/yum.log
distroverpkg=redhat-release
tolerant=1
exactarch=1
obsoletes=1
gpgcheck=1
plugins=1

# Note: yum-RHN-plugin doesn't honor this.
metadata_expire=1h

installonly_limit = 5

# PUT YOUR REPOS HERE OR IN separate files named file.repo
# in /etc/yum.repos.d
exclude=apache* httpd* mod_* mysql* MySQL* da_* *ftp* exim* sendmail* php* bind-chroot*

** Update 2 **
Results from the commands you've provided.

[root@dds ~]# rpm -q php httpd
package php is not installed
package httpd is not installed
[root@dds ~]#
[root@dds ~]# rpm -V php httpd
package php is not installed
package httpd is not installed
[root@dds ~]#