I have been trying to convince management of the benfits of moving to Zimbra from our hosted environment we have of Exchange currently. However, management still feels like Zimbra is a mom and pop shop and isn't worth looking into. How would you go about convincing upper management of to switch.

The one person in management that is not willing to budge basis is information off of the following: ( granted we only have about 75 employees )

Nobody would want to switch to the desktop/web client.
Everybody is too familiar with outlook ( even though it works with zimbra too ).
It is to much of a change for everyone.
Exchange is better and more stable. ( ha, it runs on microsoft windows )
Zimbra only has a few customers ( 15 million mailboxes, ha )

Can anyone please provide me some better information to provide management. I have tried to show the benefits. Does anybody have any any executive white papers that can be presented.