Justification for Zimbra

[hmmblah]

I've decided to roll out Zimbra where I work. The problem is I don't have final say, a board of directors does. I know my reasons for justification vs other products such as mdaemon, Exchange, & Groupwise.

Are there any sites out there that do a feature by feature comparison of the different e-mail servers? I did spend quite a bit of time googling, but didn't find anything useful to present to a board. Unfortunately, I can't use price because mdaemon is cheaper, but lacking features. I'm already going to use the Archiving and Discovery add-on as part of my argument as well as mobile push for smartphones. Customization through Zimlets is another argument I will use.

Anyone else here have to deal with a similar situation?

Thanks.