Software

I have a few users who are over 10 GB each. The *average* mbox size is over a GB.

Now, picture 700 users and a small backup window with a short recovery window...

If there is a good business reason for keeping EVERYTHING, then just make sure your systems are built to handle it. If not, explain the cost/performance ratio to the boss(es) and let them decide.

But let me just say, please get at least another server. It's not good architecture to put all of those services on the same machine.

...until you have some BIG mailboxes. Most importantly: limit the mailbox sizes of your senior managers and your marketing department. Managers "never have time" for mundane tasks like organizing their mail, and marketing departments always fill their mailboxes with huge video clips and images.

Before I cracked down on mailbox size, we had 3 users who accounted for 35% of the space on my Exchange server: two senior managers and our marketing person.

You won't need to limit your technical people; they organize things by nature. Half of them have probably already set up multiple PST files with personal files on their hard drives and work files on their home network folder.

Senior managers are not technical people. Even if they were professional engineers at one point, a few years of management will dull anyone's senses to the point where all they can understand is meetings and org charts. Limit their mailboxes, and tell them there's a technical problem that will not allow their mailbox size to be any bigger, and by the way you need a new RAID-5 array because the platters on the old one are getting dusty.

if you have bigger stores then you should be better in managing hardware storages usually a bigger store cause of performance degradation.
Consider too for backup jobs and data recovery when there is a trouble, how long it takes down time to restore and time to execute backup of the stores. I think you should limite mailbox sizes even for a CEO, just give the appropriate size according to their position and their need.

I think that is exchange suicide.
You should get in the practice of putting limits on the mailboxes. There are several reasons why you should do so.
for example if your users want to access remotely over a vpn, syching 3 gb mailbox will take forever. I cannot imagine if you have to recreate the profile for auser that you might have to do a sometime. the time it will take for all those emails to populate the mailbox will take a long wait.

I think would not see the slow downs because you got 40 users once you expand you alot more users come onboard there you will see performance issues.

I would suggest give a limit of 50MB - 100MB and have your users save to PST files for emails they want to archive and map the pst to a mapped drive to a server for storage then run shadow copying on the server.

That solution would be sweet in my opinion.

If you limit mail box's it doesn't have to be 500MB you can keep control of your storage. It also protect against spam and mail bombattacks, if you remove the limit bang there goes all your space, and your exchange server dies.

If one user sends an email with a 10MB connection and they send it to 10 people you have stored 100MBytes in very little time, now if they all resend it to 10 other people you now have 200Mbytes for just one email and one attachment. they they modifiy or add to the attachment then resend it back to the ten people, you now have 300Mbytes, you should be getting the idea. bad stuff can happen very quickly. set up an archiving system save old emails, start using pst files as well.

to take into account yahoo's 1GB mailbox size for their FREE email service.
and Google's 2GB mailbox size for GMAIL accounts.

with the stupidity of people in sending massive multimedia emails you do need larger mailboxes than the old standard of 5 MB.
[ naturally, I detest multimedia emails and concider them spam, no matter who they are from ]

I have close to a gig of plain text emails in my own system, as an email archive from several email lists. the limits do stop people from emailing ripped dvds but then no-one seems to be quite that stupid..yet.

editing to add:

multimedia email includes HTML email