Hosting Email

How do folks handle email for their web startup?

I have my rails app handling all of its email chores beautifully using sendmail and ActionMailer. New Account Confirmation, Forgotten Password Email, Monthly Newsletter, etc. DNS points to our server using MX records and we're good to go.

My issue is how do I handle my corporate email -- employee email, etc? I would really like to use google's private label hosing capability (i'm talking about google hosting johnsmith@mysite.com NOT johnsmith@gmail.com) as the Mail User Agent (MUA). However, I can't figure out how to get employee mail to bypass our web app and go to the Mail User Agent while still maintaining the MX record link to our web app for the web apps business(again, preferably google's corporate email handling).

It's as if I need two sets of MX records -- one for the web app traffic and one for our corporate/employee email.

What have other folks done? Am I missing something fundamental? For example, is there a way to have sendmail accept all email but then bounce the employee email over to an outside MUA (again, maybe google)?