by Michael B. Smith MCSE/Exchange MVP

Way back in the dark ages, when Exchange Server was originally released, every Exchange database had a limit of 16 GB. That didn’t last long. By Exchange 5.5, Microsoft had split the Exchange product into a Standard Edition and an Enterprise Edition. The Standard Edition retained the 16 GB limit, but the Enterprise Edition could have databases of any size. Of course, the practicality of this was limited by the speed of backup and recovery available and the SLAs (Service Level Agreements) that an IT organization had with its customers.

Starting with Exchange 2000 Server, Microsoft allowed the Enterprise Edition of Exchange Server to have up to twenty mounted mailbox databases per server (with the Standard Edition still limited to a single mailbox database per server). This particular limit stayed the same in Exchange Server 2003. In Exchange Server 2007, the Standard Edition can now have five mounted mailbox databases and the Enterprise Edition may have up to fifty mounted mailbox databases.

Another important change happened for Standard Edition beginning with Exchange Server 2003 service pack 2. As of that service pack, Microsoft removed the 16 GB limit from the mailbox store and allowed it to grow as large as 75 GB (with a registry change – see KB 912375 - How to increase the Exchange Server 2003 Service Pack 2 18-gigabyte database size limit). In Exchange Server 2007, the database size limit was removed from Standard Edition completely.

Now, with Exchange Server either edition, the size of your mailbox databases is limited by your backup and restore timeframe. Remember, if you have to do a mailbox database restore to a live database – your users are down while the restore is happening and while the log files are replaying. Downtime should be minimized as much as possible.

So, while you should always protect yourself by taking database backups, and you should always verify that you have good backups, the real goal is to only have to use those backups in a “disaster recovery” situation. That is, heaven forbid, your data center is flooded, or something physically destroys your Exchange Server.

Exchange and Outlook, working together, provide mechanisms for assisting in reaching this goal. They are called Deleted Item Retention and Deleted Mailbox Retention. These values are configured on each mailbox database. With these features and a little user and administrator training, you will probably never have to execute that database restore!

Whether using ESM (for Exchange Server 2003) or EMC (for Exchange Server 2007), you set these attributes on the property sheet for a specific mailbox database. I recommend that you set both values to 30 days, if possible, but for a minimum of 7 days.

Note that once you set these attributes, that items are not physically deleted from your mailbox database until after XX days have passed, where XX is the number of days for which you configure the attributes. This can cause the disk space requirements for your mailbox database to significantly expand, as well as increase the size of your backup media requirements.

Finally, if your users are using Outlook 2003 with RPC/HTTP, you should refer to KB 886205 - Deleted items are not available after you use "Recover Deleted Items" in Outlook 2003, and make the change recommended there.

Using the Recover Deleted Items functionality is easy. An overview of it (which applies to Outlook 2003 and Outlook 2007) is available at http://technet.microsoft.com/en-us/library/aa997155.aspx.

While there are no guarantees that this will always work, using this technique should minimize the necessity for ever restoring that mailbox database from backup.

How to increase the Exchange Server 2003 Service Pack 2 18-gigabyte database size limit
http://support.microsoft.com/kb/912375

Deleted items are not available after you use "Recover Deleted Items" in Outlook 2003
http://support.microsoft.com/kb/886205

Every now and again someone asks about the "Outlook is in Recovery Mode" error. This error comes up for cached (or offline) users after the administrator recovers a mailbox or does other maintenance work on the mailbox stores and gives the user the option to continue, work offline or cancel. When the user selects continue, Outlook loads ok and all seems well, but the message keeps popping up until the problem is addressed.

This error means Outlook detected differences between the cached copy of the mailbox stored on the local computer and the copy that is stored on the Exchange server. The solution is to start Outlook in online mode (by disabling cached mode) then quit Outlook and re-enable cached mode.

Question: When I deselect calendars in Outlook, the calendar name in the Title bar (and on the task bar button) continues to show the deselected calendar's name.

Answer: You don't mention which version and the exact behavior varies between Outlook 2003 and 2007. Generally speaking, the last calendar selected populates the title bar and you need to refresh the view by going to another module and coming back to the calendar to change the displayed name.

In Outlook 2003, it’s the last calendar selected in your default mailbox. If the calendars in your mailbox are unchecked, then it’s the last calendar selected. Outlook 2007 uses the last calendar selected, regardless of where its stored.

You can control what Outlook does after moving or deleting a message. Go to Tools, Options, Preferences tab, Email Options. At the top is the option "After moving or deleting an open item" with choices to open the previous item, open the next item or return to the Inbox.

While the dialog says "open items" the setting also applies to items selected in the message lists. You can use this setting to control whether you move up or down the message list as you delete items.