MS Exchange Email not sending or receiving after uninstall/reinstall of SMTP service? Link to Postini broken maybe?

I think I broke an Email server on Friday....  I was trying to setup Email notification for Veritas BackupExec and when the test messages weren't sent, well, without thinking it through I uninstalled and reinstalled SMTP service from Add/Remove Windows Components.  Since then it seems that no mail is getting in or out.

I don't have remote access to this server (I did briefly yesterday) so I'm not sure I can provide enough specific info here but I will be heading into Manhattan tomorrow to try to sort things out and I'm hoping someone out there will be able to point me in the right direction.  The server is Windows Server 2003 (SBS?) and it's running Exchange 2003 Standard SP2 through Postini.  My guess is that the configuration for Postini is gone, and I put a call in to them yesterday but have not heard back yet (no weekend support?  What up wit' dat?!?).  Anyway, I have limited experience with Exchange and zero experience with Postini...

The Exchange services are all started, the server was re-booted, and the Information Store is mounted and stays up.  Outlook clients are able to connect and see their existing mail, but nothing new has come in or gone out in two days.  There were some SMTPSVC 4000 and 4006 entries in the error log when I was able to connect in and look at it, as well as MSExchangeMTA entries that I don't recall the # for at the moment....

My two questions are these:  One, how do Exchange and Postini work together?  Where are the settings/configuration for this integration stored in the default/basic configuration?  And two, what are the basic troubleshooting steps I will need to use to determine where stuff is getting stuck?

Quite honestly, I'm in way over my head here and any help is greatly appreciated.