Email application with notifications only for specified contacts (standard SMTP/POP3/IMAP)
I haven't found a standalone app but K9 in conjunction with WhoIsIt Lite supports this. It doesn't do away with visual notifications mind you, but it can silence them.

Alternatively you could investigate whether your workplace email support server based rules. You could use them to filter unimportant emails into a folder other than your inbox. Android's stock email app only checks for new emails in your inbox so the app would ignore the others.