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How to override the attachment size limit for OWA public folder posts

The maximum size limit of any attachment posted to an OWA public folder is 1 MB. If you don't want such a small cap on attachments, here's how you can override the size rule through the registry.

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Uploading attachments bigger than 1 MB to Outlook Web Access can cause bottlenecks in your network or the Web server itself. So the maximum size limit of any attachment posted to an OWA public folder is 1 MB -- this is true even if there are no limits set on the public folder store itself.

If your company doesn't want such a small cap on attachments, you can override the size rule in OWA:

  1. Open the registry on the computer where Microsoft Exchange is running and navigate to:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ MSExchangeWEB\OWA.

  2. Under OWA create a new DWORD named Message Size Limit.

  3. Set Message Size Limit to the number of kilobytes you want the maximum attachment size to be. For instance, if you set this value to 2048 (decimal), a maximum message size of 2 MB will be enforced.

  4. Restart the Exchange Server information store.

OWA doesn't enforce a strict upper limit for this value, but anything over 10 MB is probably impractical. If you have people routinely posting large files to public folders, you may want to retrain them to use an FTP site or a shared server folder instead. HTTP isn't really designed for delivering or receiving large files in bulk.

For the above procedure to work, you need to be running either Exchange 2003 (any version) or any service pack revision of Exchange 2000 that has been updated with the post-Service Pack 3 update (as described in Knowledge Base article 870540).

About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter.

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Related information from

  • FAQ: Outlook Web Access
  • Tip: Troubleshooting Outlook Web Access
  • Reference Center: Public Folder Management

  • Dig Deeper on Outlook management