The disagreeable deeds of monitoring messages and setting size limits

A Microsoft Exchange Server administrator's list of unpleasant tasks is usually pretty long. Among these distasteful but often necessary chores is one genuine horror: policing mailbox usage. On the day when a dreaded message management task finds its way to your to-do list, you'd best be prepared.

How Big Is Too Big?
The need to manage Information Store (IS) size is inevitable because Boyle's Law also applies to email: Like gas, email data always expands to fill available storage space. Suppose your average user's mailbox size has expanded to 100MB. If you have 300 users on an Exchange Server 5.5, Enterprise Edition (Exchange 5.5/E) system, your private IS is roughly 30GB. If your backup subsystem can back up 7GB per hour, you need approximately 4 hours to perform a complete backup and 8 hours to complete a restore (restores typically take about twice as long as backups).

Is 8 hours too long? Whether shutting down an email server for a day is catastrophic or merely inconvenient depends on your environment. If your IS becomes so big that backup and restore operations become a burden to users, you have a few options for fixing the problem: You can invest in better backup hardware, move some users to another server, or migrate to Exchange 2000 Server and use its multiple databases and storage groups (SGs) to divide your backup and recovery load. But the easiest—and probably least expensive—solution to IS overload is to limit users' mailbox sizes.

The problem with mailbox size limits is that users hate them. However, you can counter users' objections with rational explanations: Limiting mailbox size might let you avoid buying more hard disks or servers, thereby saving the company money; reducing mailbox size also reduces the time the server needs to be down for restores, thereby improving user service.

Most sites that use this tough-love solution set size limits between 50MB and 100MB and increase these limits for employees whose job functions demand more mailbox space. I can't recommend a one-size-fits-all limit because users' needs and hardware capabilities vary.

Applying Mailbox Limits
After you convince your friendly population of understanding users that mailbox size limits are a good idea, the mechanics of imposing those limits are straightforward. In Exchange Server 5.5 and later, you can apply limits to individual space hogs' mailboxes or you can apply a limit to the IS.

Imposing a size limit on an individual mailbox is simple. Open Microsoft Exchange Administrator, and select the mailbox. Right-click the mailbox, and choose Properties. Go to the Limits tab, which Figure 1, page 82, shows. The Information store storage limits settings govern how large the mailbox can get before Exchange takes the following actions:

  • Issue warning simply sends the user a gentle daily reminder that he or she needs to clean up his or her act. You can't modify the warnings that System Attendant sends users, although Microsoft Consulting Services will be happy to sell you customized messages.
  • Prohibit send causes the IS to reject any messages the user sends. Exchange then returns a nondelivery report (NDR) to the sender. This limit is more of an annoyance than an active measure; Prohibit send doesn't keep the user from receiving mail, so the mailbox keeps growing. Also, this limit doesn't prevent users from sending mail through IMAP or POP because IMAP and POP messages usually don't go through the IS.
  • Prohibit send and receive is the big daddy of limits. Users can't send or receive mail until they bring their mailboxes under the size threshold you've set. All users can do after this limit goes into effect is read (and hopefully delete) messages already in their mailboxes.

You can also set these limits for all mailboxes in a private IS. In Exchange Administrator, expand the server and select the IS you want to modify. Right-click the IS, and select Properties. You set limits on the General tab. Individually imposed mailbox size limits override these IS-wide limits.

You can apply limits to several Exchange Server 5.5 mailboxes at once without applying limits to the entire IS. Simply generate an export file, edit it to contain only the mailboxes you want to limit, and add the appropriate limit to the .csv file (both in the header and in each record for which you want to apply the limit). Reimport the file, and presto!—you're finished. (For more information about the proper use of directory import and export, see "Super Export and Import Tools," August 2000.)

To customize the intervals at which System Attendant scans mailbox sizes and sends warnings, open Exchange Administrator and the Information Store Site Configuration object's Properties page, and click the Storage Warnings tab. The default interval is once a day, but you can select the time of day or select Always for Exchange Server to check limits approximately every 15 minutes.

In Exchange 2000, you can apply limits to individual mailboxes, to a mailbox store (the equivalent of Exchange Server 5.5's IS), or to all mailbox stores in an SG. Individual mailbox limits take precedence over mailbox store limits, which in turn take precedence over SG limits. You can also use Exchange Server system policies (not to be confused with Windows 2000 group policies or Windows NT system policies) to apply limits to all mailbox stores on a particular server. For the lowdown on how to create and manage Exchange Server system policies, see the Microsoft article "XADM: How to Create System Policies in Exchange 2000" (http://support.microsoft.com/support/kb/articles/q256/1/41.asp). For more information about limiting mailbox size, see Tony Redmond, "Mailbox Management," October 2000.

Watching Email Go By
Most Exchange Server administrators also dread the day when management asks—or requires—them to read someone else's email. Ethical concerns aside, if you open another person's mailbox without written direction from a company officer, you're being foolish. Better yet, rather than read someone's email on a manager's behalf, enable the manager to do the deed directly.

Granting management read-access to a suspect mailbox is easy to do but difficult to do discreetly. Another option is to turn on Message Journaling. Exchange Server 5.5 Service Pack 1 (SP1) first introduced this feature, which lets you copy a server, site, or organization's inbound and outbound email traffic and send it to a mailbox or public folder. Message Journaling copies all traffic (excluding SMTP messages from POP3 or IMAP4 clients). You can enforce a rule to throw away any email not to or from the suspect, or you can surreptitiously move the user in question to another email server (some sites keep around an old server for exactly this purpose). Turning on Message Journaling is straightforward: You need to add a few registry keys to the IS, Internet Mail Service (IMS), and Message Transfer Agent (MTA). The Microsoft article "XADM: How to Enable Message Journaling in Exchange Server 5.5" (http://support.microsoft.com/support/kb/articles/q239/4/27.asp) describes the process.

Surprise! Exchange 2000 uses a different name for Message Journaling: message archiving. You use message archiving to control an SG's individual databases. Simply open Exchange System Manager (ESM), select the mailbox store for which you want to enable message archiving, right-click the database, and select Properties. From the General tab, which Figure 2 shows, select the Archive all messages sent or received by mailboxes on this store check box. Click Browse, and select the contact, mailbox, or folder that you want to receive these messages.

Message Journaling and message archiving can also be useful to administrators who need to formally archive email traffic for the long term. For more information about archiving techniques, see "Managing Messages," June 2001.

Unavoidable Chores
No one—well, hardly anyone—likes managing messages. Most administrators see message management as akin to making children clean their bedrooms. Often, implementing message management hurts you more than it hurts your users. But the task must be done, and a little painful but proactive attention to your mailboxes might postpone the need to add another dreaded task—buying more Exchange Server storage—to your to-do list.