There have been some places pop up that support the older RH.  Try the 
Fedora Legacy project.  I believe they compile security updates and 
maintain a repository online that you can point apt or yum towards.

When I was looking for a webmail prog. I really like the NeoMail 
project, but due to a contract the developer signed w/ his new employer 
he had to stop development.  BUT, the code was picked up and continued 
w/ a new name, alas I can't remember the name.  Neomail I see has been 
continued under the old name also here: 
http://www.neocodesolutions.com/software/neomail/
and still avail. for download on sourceforge.
If you want more features, like the Horde, there are several groupware 
projects, like PHPGroupware, OpenGroupware and others.  They provide 
calandering, shared and private file server space, webspace, notes, etc.

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Somewhere there is a village missing an idiot.