Problem solve Get help with specific problems with your technologies, process and projects.

Set storage limits for Exchange public folders

Concerned about your public folder store size outgrowing your Exchange Server? Here are some guidelines for determining how to put a limit on folder size.

If your company uses public folders for information archival, the folders will eventually become too large for...

the server to handle unless they are regulated.

Exchange Server 2003's public folder store has a 16 GB size limit. While the 16 GB limit has been removed in Exchange Server 2003 Enterprise Edition, there is a practical limit to how big the public folder store can or should get.

The practical limit comes into play when you need to perform a backup or a restore operation. The folder's size also affects the server's performance--once a public folder exceeds 35 GB, the server's performance tends to start diminishing. Even if performance were not an issue, you must always make sure that the volume where the public folder store resides has enough free disk space to perform a restore or database recovery operation should it ever become necessary.

Restore and recovery operations require that the volume containing the store have an amount of free disk space equal to the folder's size, plus 10 percent. That means that if you were to limit the public folder store size to 35 GB, then the volume containing the store should have a total size of approximately 75 GB minimum with at least 40 GB of free space.

Obviously, it is important to regulate public folder usage so that your server does not run out of disk space or perform poorly. Unfortunately, I can't tell you exactly what kind of limitations to place on your public folders because every company's needs are different.

When planning for public folder regulation, there are several elements you need to consider. Some of the questions you should ask yourself are:


  • How many folders do I currently have?
  • How big are those folders now?
  • Does the content of those folders regularly expire?
  • Will any new folders be created in the foreseeable future?
  • What is in those folders?
  • Are items stored in the Deleted Items portion of the folder or are posts removed immediately? (This is important because deleted items count toward the folder's size.)

Apply limits to public folders
Microsoft recommends creating a blanket set of limits that apply to all public folders and then overriding those limits on individual folders where necessary.

If you have too many individual folders that would require overrides, you might consider creating multiple public folder stores and placing a different set of restrictions on each store according to the folders within the store. If you choose to use this approach, however, remember that older versions of Outlook are only capable of viewing a single public folder tree.

To place a set of limitations on a public folder tree, open the Exchange System Manager and navigate to Administrative Groups | your administrative group | Servers | your server | First Storage Group | Public Folder Store. Right click on the Public Folder Store container and select the Properties command from the resulting shortcut menu. When you do, you will see the folder tree's properties sheet. Now, select the Limits tab.

The Limits tab is self explanatory. It allows you to set various thresholds as well as the maximum folder size. You can also control how long deleted items are retained and set an age limit for posts within the folders. Keep in mind that the age limit is based on when a post was most recently modified, not necessarily on when the post was created.

One positive aspect of public folders is that unless you are using them to store files, they tend to be rather small because they contain plain text. Microsoft recommends setting a 20 MB limit to simple, text-based public folders and a 100 MB limit if the folder is text based and used for long-term archiving. While these values are certainly not appropriate for every situation, they do make for a good starting place.

Some folders need 'overrides'
After setting the blanket folder limits, you will most likely want to override those limits on certain individual folders. For example, if you have a contacts folder that you use as a company directory, then there is a good chance that the posts in that folder never expire. You will want to override any age limits that you might have set. Likewise, if you have a folder containing numerous files, then a 20 MB size limit is probably way too small for that folder. You need to set up an override to either remove the size limit or to set the limit to a more appropriate size.

Setting up overrides on individual folders is very similar to setting the initial blanket limits for the public folder store. To do so, go back to the Exchange System Manager and expand the Public Folder Store object. Now, select the Public Folders container to reveal the folders stored on the server. Right click on an individual folder and select the Properties command from the resulting shortcut menu. When you do, you will see the folder's properties sheet. This properties sheet contains a Limits tab that is identical to the one that you saw earlier. The only difference is that you are now setting limits for a single folder rather than for every folder in the store.


Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. Brien has served as the CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer he has written for Microsoft, CNET, ZDNet, TechTarget, MSD2D, Relevant Technologies and other technology companies. You can visit Brien's personal Web site at


Did you find this tip useful? It first appeared in the free newsletter, Exchange Adviser. Sign up now so you can receive the Exchange Adviser, which is filled with technical articles, expert advice, news and everything Exchange!


Do you have a useful Exchange tip to share? Submit it to our monthly tip contest and you could win a prize and a spot in our Hall of Fame.

Dig Deeper on Exchange Server setup and troubleshooting