Exchange 2007 - OWA attachment size limit

When using large attachments (larger than 30 MB) with OWA in Exchange 2007 you will get an 404 Error message during upload. This is due to IIS preventing large streams of data (which potentially leads to a denial of service possibility).

If you need to enable larger attachment sizes then you can do the following:

• Logon to your CAS-servers
• Browse to the OWA directory
  Default: C:\Program Files\Microsoft\Exchange Server\ClientAccess\Owa
• Take a backup of the current web.config file
• Edit web.config
  Need to edit the existing (the size is in kilobytes) - 60 MB = 60*1024 = 61440 kB
• Start a command prompt (elevated)
• Browse to your iis directory
  Default: C:\Windows\System32\inetsrv
• Run the following command: appcmd set config "Default Web Site/Owa" -section:requestFiltering -requestLimits.maxAllowedContentLength:xxxxxx (where the size is in bytes) - 60 MB = 60*1024*1024 = 62914560 bytes
• Command prompt: IISReset

Default sizes - web.config

• OWA: 30 MB attachment limits (30000 in web.config)
  C:\Program Files\Microsoft\Exchange Server\ClientAccess\Owa\web.config
• EAS: 10 MB attachment limits (10240 in web.config)
  C:\Program Files\Microsoft\Exchange Server\ClientAccess\Sync\web.config
• EWS: 13 MB attachment limits (13280 in web.config)
  C:\Program Files\Microsoft\Exchange Server\ClientAccess\exchweb\ews\web.config

Links

• http://technet.microsoft.com/en-us/library/aa996835(EXCHG.80).aspx
• http://support.microsoft.com/kb/953526
• http://technet.microsoft.com/en-us/library/aa996373(EXCHG.80).aspx