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Outlook: Optimizing Outlook for Low-Bandwidth Performance

How can I optimize Outlook for low-bandwidth performance?

You can set a few registry entries to configure Outlook to work more efficiently when you're dialing in or when you're experiencing high latency (e.g., with satellite connections). If you give the HKEY_CURRENT_USER\
Software\Microsoft\Office\10.0\Outlook registry subkey entry DisableBGSave of type REG_DWORD a value of 1, Outlook won't stream file attachments to the Exchange server when you're composing a message. For more information about this change, see the Microsoft article "OL: How to Disable the Background Transfer of Attachments to the Exchange Server" (

If you open a digitally signed or encrypted message, Outlook's default behavior is to consult the Certificate Authority's (CA's) certificate revocation list (CRL) to verify the sender's authenticity. However, Outlook might appear to hang as it downloads and opens the CRL file. To disable CRL checking, set the HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook\Security subkey's UseCRLChasing entry of type REG_DWORD to 2. To reenable the feature, give the UseCRLChasing entry of type REG_DWORD a value of 1, the default. To configure CRL checking to work only when you're online, set the value to 0. For more information about these changes, see the Microsoft article "OL2002: Performance Problems When You Open Digitally Signed or Encrypted Messages" (

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