Large Mailboxes Are Here to Stay

Microsoft touts Exchange 2007's ability to support large mailboxes because of the larger memory model made possible by the Windows x64 platform. Having large mailboxes will certainly please the human pack rats that populate many Exchange servers, but the growth in mailbox size does pose some management challenges. Exchange 2007 will make managing large mailboxes easier, but what can you do until then?

The Super Size Phenomenon
Mailbox sizes have steadily increased from the 25MB quota that was commonly allocated for Exchange Server 4.0 deployments to today's generous quotas of 250MB?500MB. Users argue that the time they spend keeping their mailboxes within a strict company-imposed size limit, coupled with the low cost of storage, makes it more cost effective for companies to simply allow larger mailboxes. The result is that many large mailboxes are in use today, some of which approach 20GB.

Of course, users like large mailboxes and have a tendency to use all the space you give them. But regrettably, some features of email clients, such as the Reply All option and the way Outlook lets you include previous messages in a mail thread, cause users to fill their mailboxes even faster than necessary. Using Microsoft Word instead of a simpler editor also contributes to large mailboxes, as does using graphics in auto signatures on every message.

Don't get me wrong. I like Outlook and consider it a good email client, but it could use some tweaking to encourage better email habits in users. Outlook 2003 and Outlook 2007 let users reduce the size of graphics attachments through compression, but extra intelligence, such as automatically stripping auto signatures in message threads, would help, too.

Kicking the PST Habit
Although large mailboxes are hard to manage, they provide an advantage by allowing organizations to move away from personal folder files (PSTs) to server-based storage. Satisfying compliance requirements is easier when email is online and stored in user mailboxes on a server than it is if email is saved in a mixture of online mailboxes and PSTs. Compliance is difficult if you can't attest to the email that users control.

There are other reasons for moving away from PSTs as well. Server-based virus scanners don't scan PSTs, and users can waste space by saving copies of messages in multiple PSTs. Spreading messages across multiple PSTs could compromise security, too: Even if your PSTs are password protected, a knowledgeable hacker using a password cracker could gain access to your PSTs within seconds. Because of the security implications, I strongly recommend eliminating the use of PSTs in your organization.

Is Super-Sizing Really Better?
The disadvantages to large mailboxes include having to manage more storage and determining how to effectively distribute users across databases and storage groups (SGs). Exchange 2007's larger memory model and its ability to manage more databases should make it easier to support and manage large mailboxes.

On the client side, if you use Outlook 2003 in Cached Exchange mode, you might notice that performance degrades when your mailbox size exceeds 1GB because the offline folders file (OST) on your local hard disk has to do a lot of work to process new messages. Microsoft didn't design the OST to handle large mailboxes, and its inherent inefficiency is compounded by the slow speed at which hard disks in laptop computers process I/O operations.

Analysis Tools for the Interim
While you're waiting for Exchange 2007 to arrive, you can do a few things to gain some control over the size of user mailboxes. Before you increase mailbox quotas, you should understand who the heaviest email users are and how they're using messages on your server. Here are some tools that can help you monitor mailbox activity.

Helpful Information for the Future
Now is always a good time to start tracking email usage data. Understanding how users send, receive, and store messages on your servers will help you predict future storage requirements and make an educated decision about the size of mailboxes you need to support now and in the future.