The page here: https://blog.totalcomputing.co.uk/2007/06/installing-mail-for-exchange-on-nokia.html

Describes how to get mail for exchange ( a nokia app) running on the N95

First install 1.3.1 and enter all your settings, and do a full sync.

Now update to 1.5.0, the reason for this is that once 1.5.0 is installed non of the settings can be changed.

I am yet to give this a go on my N95 8GB, but will post an update once I have.

UPDATE: Download version 2.5.5 here