Error FQDN, Please configure Fully Qualified Domain Name

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Hi i am using CentOS 6.2, 64 bit, i have installed following

1. Openldap 2.4
2. Apache 2.2
3. PHP 5.3
4. Postgresql 9.2 Standard

Hostname : Server1.example.com

/etc/hosts

192.168.10.100     mail.example.com mail
192.168.10.100    ldap.example.com ldap
192.168.10.100    php.example.com php

while i am running sh iRedmail.sh then i am getting below error
<Error> FQDN, Please configure Fully Qualified Domain Name

What could be the possible cause of this error and how to get rid of this error ?

Thanks in advance.