I currently manage an Exchange 2003 server with 25 mailboxes. Several users have 4GB+ mailboxes including the CEO. The total Message Store is 35GB. I use Postini for anti-spam. We are in the process of transitioning to Google Apps Message Security for anti-spam. Google has notified me that the transition should be complete within the next two months. We do not use public folders.
I would like to have a redundant solution in place so that when/if the Exchange server goes belly up there will be little to no down time at a reasonable cost and low administrative overhead. To that end, I have been looking at Google Apps Mail as a means to keep our current Exchange environment but also have redundancy. I would like to test Google Apps with three users before implementing it for all 25 users with external mail. My reading of Google documentation leads me to believe it is doable with a combination of "split" and "dual" delivery. However, this would be using "legacy routing controls". I am not clear how to do this using Google's "Mail routing and delivery: Guidelines and best practices".
I would like to find a step-by-step guide to setup Google Apps Mail as described. Any help is greatly appreciated. I will also be happy to take suggestions for alternative products for redundancy and possible future road map.
Legacy Routing Controls
Mail routing and delivery: Guidelines and best practices