Free/Busy Folders in Exchange Server 2003 in Depth

Free/Busy Functionality in Detail

The free/busy data is nothing more than any published information of a user’s availability data based on the user’s schedule. Exchange Server 2003 uses this information when users are scheduling meetings. This feature provides an explanation of how clients such as Microsoft Office Outlook 2003 work with Exchange Server 2003.

All free/busy information is stored in a dedicated system folder called SCHEDULE+FREE BUSY. This folder contains a separate subfolder for each Exchange administrative group. When a user publishes his free/busy data, Exchange posts this information in a message in the appropriate subfolder that now functions in a manner similar to the offline address book folders.

If you want to have a look at this folder you can view the node by using Exchange Server 2003 System Manager by switching to System Folders.

If you are planning a migration from one Exchange Server to another you should never forget to replicate this system folder to make sure that any free/busy information will still be available.

By default, Outlook publishes the free/busy data for a user once every 15 minutes and again when Outlook is being shut down. Every message includes the entire free/busy information for the corresponding user that ranges from the current month to two months in the future. If you want to change this behaviour you can do this in Outlook general properties. The only thing you cannot change is the setting where you can’t publish any information apart from the current month, because it is hard coded.

Figure 1: How the Free/Busy Feature works

Outlook Web Access and Outlook Mobile Access do not publish any free/busy data directly. Instead they rely on a free/busy publishing agent that is called MSExchangeFBPublish with runs as a part of the System Attendant Service. Its two functions are:

  • Publishing free/busy data
  • Deleting duplicate free/busy messages

Figure 2: The MSExchangeFBPublish Agent

Free/Busy Functionality between different Exchange Organizations

If you have different Active Directory Forests and therefore different Exchange Organizations in your network environment, you will need to use free/busy information between these Exchange Organizations. This is where you need the Inter-Org replication utility. This tool provides the following functions:

  • Directory synchronization
  • Free/busy replication

If you have successfully configured this tool it pushes free/busy information from one Exchange organization to another using the MAPI protocol, which means that it is not an Internet-friendly solution and should be only used via secure VPN connections. And be careful: the inter-organizational replication process is one-way. To establish two-way replication, you must configure replication separately for each Exchange organization.

The replication uses the following steps:

  1. Identification of a list of changes that need to be exported from the source public folder store and the current status of the destination store
  2. Propagation of the changes to the destination public folder store

If it is unable to create the destination item in the corresponding folder, it will delete the source item to maintain synchronization. If an item has been deleted and public folder tomb stoning is enabled, the item cannot be created again and replication will not occur properly.

Free/Busy Functionality between Exchange and Non-Exchange Systems

If you want to configure free/busy functionality between Exchange and non-Exchange Systems, you will need to use the Exchange Server 2003 Calender Connector that supports Notes Domino Server and Novell GroupWise.

Figure 3: Installing the Microsoft Exchange Calender Connector

This connector covers the following topics:

  1. Replication of directory information so that all users have access to the corresponding calendar data
  2. Conversion of meeting request item formats from Exchange to the foreign format and vice versa.
  3. Detection of Exchange Server 2003 free/busy requests and look up of these data in foreign systems – this process is bidirectional

If you are using the Exchange Calender Connector with Notes Domino you should know that a clustered domino environment is unsupported, because the connector looks for a database named busytime.nsf. This database name is only available if you are not using a domino cluster!

Free/Busy Functionality Troubleshooting

a) in Outlook:

If you are considering problems with the free/busy information published in your messaging environment, you should know that it is possible to run Microsoft Office Outlook with the /cleanfreebusy switch.

The technique behind this switch is that Outlook maintains a hidden message that is called LocalFreeBusy in each user’s calendar folder. This message is only relevant to the mailbox owner and delegates of that mailbox. If a delegate user re-creates the LocalFreeBusy message, which is then not synchronized with the rest of the calendar data, an error message may occure stating “unable to open the free/busy message”. The corresponding switch recreates the LocalFreeBusy message to maintain integrity.

b) on the Server:

If your free/busy system folder becomes corrupt or is missing you will have to do some more troubleshooting.

As already stated, the tool MSExchangeFBPublish agent (or MadFB) has the function to clean up the existing free/busy data. By default, this cleanup runs at 2:00 a.m. every morning on each server with a mailbox store. It now identifies the corresponding system folder and deletes duplicate and if possible repairs the URLs of free/busy messages.

If the complete SCHEDULE+FREE/BUSY folder is missing you will have to do some more steps as described at;en-us;284200.


With this in-depth knowledge of the Exchange Server free/busy feature you will now have the complete understanding of how to deal with this feature properly. As you have seen the process behind it is quite easy. In my own consultancy experiences the problem itself often is that nobody really knows what this public folder is really for or that there even is one. As you can see – a problem with the free/busy folder functionally is very easy to deal with if you know the appropriate steps to do so.

If you still have any further questions, please do not hesitate to contact me.

About The Author

Leave a Comment

Your email address will not be published. Required fields are marked *

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Scroll to Top