E-mail server settings and credentials has to be set seperatly in the purechat.config.

Why not use the basic mailSettings in the web.config of the web site ?

Ex.:

<system.net>
        <!--Mail settings -->
        <mailSettings>
            <!--
            <smtp deliveryMethod="Network">
                <network host="localhost" port="25" defaultCredentials="true"/>
            </smtp>
            -->
            <smtp deliveryMethod="SpecifiedPickupDirectory">
                <specifiedPickupDirectory pickupDirectoryLocation="C:\Inetpub\mailroot\Drop\" />
            </smtp>
        </mailSettings>
    </system.net>

That way there is only one place to maintain these settings, and you have more features, like specifiedPickupDirectory for testing purposes.