Sharepoint can search  Exchange Public Folders so if all emails are moved to the folders they can be searchable

SharePoint Portal Server can search  Exchange public folders but woul
don't have this functionality if the client  just wants to use
Windows SharePoint Services (WSS) without Portal Server.

I don't know how much effort your client is willing to spend but it
would not be too difficult to programmatically read the items from
the Exchange server using CDO or MAPI and then use the SharePoint
object model to create  a list item  for each message. If you have
multiple messages  for a given support  incident then you would need
to combine the information from Exchange before creating the item in
SharePoint.