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I have an exchange server which has mailboxes that are over 68GB, I understand that the maximum size of mailboxes is only 75GB which we expect to pass in the very near future. What can I do about this?

I have another license of exchange that I could install and setup, is it possible to do this and move some mailboxes on to this and essentially give myself a 150GB limit spread across 2 servers?

Another advice or helpful links would be great


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Exchange Server is not a truck. – Evan Anderson May 14 '10 at 11:18

What you can do about it is to develop a sensible approach and ensure your users do likewise. After discussing the problem with those concerned you may want to impose quotas, which will force your users to start doing some housekeeping. What you don't want to do is to let this runaway situation continue unabated.

It's an unfortunate fact that far too many people think of their mailbox as a kind of filing cabinet. This attitude has to be broken, even though you're going to annoy the crap out of your users in the process. Sometimes being a sysadmin is a bit like being an army drill sergeant - if everyone likes you you're probably not doing it right.

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+1 for " if everyone likes you you're probably not doing it right." however exchange is a filing cabinet – Jim B May 14 '10 at 18:57
@Jim B, even if one does treat a mailbox as a filing cabinet, it needs to have limits. – John Gardeniers May 14 '10 at 23:45
yes for exchange it's either 75GB or 16TB per store. The issue needs to be discussed with the business, not pushing the issue off to the users or worse yet driving them to put mail in PST files because of some arbitrary quota. If the business wants to keep every single email ever sent explain the cost and make it happen, if not determine what the policy should be. The idea that somehow this a "runaway" situation is silly. – Jim B May 15 '10 at 5:00
I'd rather have a mailbox with 34 2gb emails than one with 80,000 1k emails. There are technical and practical limits, its an email admins job to ensure that the system lives within them, not create additional arbitrary ones. I'd suggest taking a look at for a discussion on what to worry about for mailbox size issues – Jim B May 15 '10 at 5:05

Exchange 2003 stores mail and other items in an information store. Information stores are stored in storage groups. An exchange server can have 1 or more storage groups. Under exchange standard, an information store has a maximum size of 75 GB and you can have a maximum of 1 Mailbox store and 1 Public Folder Store per Storage Group. You can only have 1 Storage Group.

Given those limitations your options are:

  1. upgrade to exchange enterprise which has allows 16TB per store and you can have 5 stores per storage group
  2. add an additional server to your organization and move mailboxes to that server. The caveat to that approach is that storage requirements can double (eg that 5 MB email sent to the whole company that on took up 5 MB will now take 10 MB since it's spread over 2 stores)

  3. you could change the mailbox to a public folder by creating a public folder and moving the mail items to the public folder then assigning the public folder the address of the original mailbox. It's not pretty but it's possible

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What you need is a messaging archive solution. A 3rd party software/appliance that stores your users email in an external database and out of Exchange. That way you can keep your user's mailboxes small (like 500MB) and have unlimited long term storage.

That is what we use where I work. If you want to keep an email you move it to an "Archive Folder". Anything not in that folder is automatically deleted after 30 days.

Very large Exchange databases are trouble waiting to happen. They take a long time to back up and much more time to restore.

Here is a link to several of the top archive solutions out there:

Hope this helps


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Yes - the 75 GB limit is per Information Store on 2003 Standard SP2. I inherited a set-up with 2 Exchange servers and mailboxes split across the two servers and it worked fine for general mailboxes.

We occasionally saw strange issues with users on one server got mail delivered a few minutes later than users on the other server - but it was a very strange set-up. I ultimately replaced it with an Enterprise installation so didn't spend too long looking at those issues.

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Some downward pressure on mailbox growth needs to be applied here, regardless of the fix to the size limit. There are options:

  • Institute mail quotas. You'll have to work with your mega-users to get them under the line, and there will be pain. But if you manage to pitch the added mail costs current practices will incur at your fiduciary masters, you might get the high level buy-in needed to get them in place.
  • Email expiration and an archiving method of some kind. Exchange has the ability to expire messages older than a certain date. You don't want to do this unless you've explained to your users how to save old emails (PST files, perhaps an actual Email Archiving product). But it'll put some downward pressure on mailbox DB growth.
  • Shaming. Use a bit of custom scripting to figure out the top mail users in each department and publish them to the department heads. This kind of shaming can bring sizes down, it depends on the area.
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No, does not work.

That said, the main problem you have to start with is a 75gb mailbox - mail boxes are neither databases nor file archives. 20gb are a pretty practical limit of how large they "should" be (OST files degrade in performance then).

With 2010 (Office, not outlook) you could mount multiple mailboxes at the same time, allowing you to use one(or more) as archive and one as "live". But I would personally not go into a 75gb mailbox EVER.

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He's using Exchange 2003 - the mailbox isn't 75GB, it's the information store. – icky3000 May 14 '10 at 11:33
Unless I'm mistaken, the 75GB limit is per server in Standard Edition, not per organization. So 2 servers each with their own Information Store should be able to host a total of 150GB of mailboxes. Am I right? – joeqwerty May 14 '10 at 11:33

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