I was working on a project where our JSR 168 portlets was communicating with Exchange Server.
Later on we were asked to add a feature so that portlets can also communicate to exchange server over SSL.
For this we first enabled SSL on Exchange server ( FBA authentication on OWA and Exchange Server 2003) and then we exported certificate from Exchange server.
To make this type of communication, we were required to import the same certificate into WPS portal.
Below article helped me for importing certificate into WebSphere Portal and this made our portlets to communication over SSL with MicroSoft Exchange server.
Enabling SSL connection between WebSphere Portal and Microsoft Exchange Server