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Article ID: 208480 - Last Review: June 14, 2006 - Revision: 3.3

This article was previously published under Q208480
For a Microsoft Outlook 97 version of this article, see 171582  (http://support.microsoft.com/kb/171582/ ) .
For a Microsoft Outlook 98 (CW) version of this article, see 181406   (http://support.microsoft.com/kb/181406/ ) .
For a Microsoft Outlook 98 (IMO) version of this article, see 181532  (http://support.microsoft.com/kb/181532/ ) .
For a Microsoft Outlook 2000 (IMO) version of this article, see 197752  (http://support.microsoft.com/kb/197752/ ) .

NOTE: The procedures in this article only apply if you have installed Outlook with the Corporate or Workgroup option. With this option, you can use Messaging Application Programming Interface (MAPI) services. To determine your installation type, click About Microsoft Outlook on the Help menu. If you have the Corporate or Workgroup installation, you see "Corporate or Workgroup".

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SUMMARY

This article discusses the purpose and capacity of each of the following storage facilities used by Microsoft Outlook when running as a client to a Microsoft Exchange Server:

MORE INFORMATION

Personal Folders Files Located on Your Computer

One or more .pst files can reside on each user's computer. A .pst can be defined as your primary store or as a secondary store. A primary store means that mail delivered to the Inbox in that file and all of your other default Outlook folders, such as Calendar, Contacts, Deleted Items, Journal, Notes, Sent Items, and Tasks reside there. A .pst file can also be defined as a secondary store, which means you can move items to that file, either manually or with Inbox Rules, from your primary store.

Each .pst file can contain a maximum of 65,535 top level items, and a maximum of 65,535 items in each folder. An item is a folder, message, task, etc. Upon reaching 16,384 items, you are upgraded to a large tables format, which increases the limit from 16,384 to 65,535. The total file size of a .pst cannot exceed 2 Gigabytes (GB).

Offline Store Files Located on Your Computer

You can synchronize the .ost and your primary store so that they always contain the same information. This allows you to work offline when the server is unavailable. When you reconnect to the server, changes made offline upload to the server and mail received while offline downloads to the .ost. Only one .ost file can be used at a time.

The .ost file can contain as many root folders as you desire and each folder can contain a maximum of 16 kilobyte (KB) subfolders. The .ost has a 16 KB folder structure by default, and this cannot be upgraded to allow large tables. The total file size of an .ost cannot exceed 2 gigabyte (GB).

Mailbox Folders Located on the Exchange Server

A mailbox folder for each user is stored on the server in the same database store. The server has a capacity that varies depending on the version and edition of Exchange Server:
  • Version 4.x and 5.0: 16GB for each server's store.
  • Version 5.5, Standard Edition: 16GB for each server's store.
  • Version 5.5, Enterprise Edition: Store sizes are restricted to drive space installed and available on the server. If larger capacity drives are installed on the server, the stores can grow to the size available.
NOTE: The server administrator may limit the size of each user's mailbox folder.

Public Folders Located on the Exchange Server

Public folders reside on the server in the same database store. They contain information shared by many users. Depending upon access permissions, individual users can create, read, update, or add to the public folder. The server has a capacity that varies depending on the version and edition of Exchange Server:
  • Version 4.x and 5.0: 16GB for each server's store.
  • Version 5.5, Standard Edition: 16GB for each server's store.
  • Version 5.5, Enterprise Edition: Store sizes are restricted to drive space installed and available on the server. If larger capacity drives are installed on the server, the stores can grow to the size available.

REFERENCES

For more information about this subject, please see the following articles in the Microsoft Knowledge Base:
195435  (http://support.microsoft.com/kb/195435/EN-US/ ) What are Offline Folders and how do you use them?
156077  (http://support.microsoft.com/kb/156077/EN-US/ ) How to specify where new public folders are stored
149217  (http://support.microsoft.com/kb/149217/EN-US/ ) Microsoft Exchange message size limitations
143376  (http://support.microsoft.com/kb/143376/EN-US/ ) XADM: Storage Capacity Limits of Microsoft Exchange Server

APPLIES TO
  • Microsoft Outlook 2000 Standard Edition
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