Ok, I'm assuming you're not getting hung up on the export/import/runscript routine. If that's the case, then I'd guess LDAP is throwing you off. Here's a link to Red Hat's website that does a pretty good job describing what an LDAP server/client is, what they do for you, etc.
I don't know that there's any email client per se on Linux that incorporates sending mail, composing it, contacts list, etc. into one bundle. The exception might be Ximian Evolution. As far as I know, it's striving to be as MS-Outlook-like as possible. I haven't looked at it closely or used it. It may even come with a tool to handle what you want... dunno.