Out-of-Office messages are sent to distribution lists that are in the BCC field

When you turn on Out of Office Assistant in Microsoft Outlook, if you receive a message that does not have an address in the To or the Cc field, but it does have a distribution list in the Bcc field, an out-of-office message is sent to the distribution list that is in the Bcc field.

To resolve this problem, you can modify the out-of-office message generation behavior on the Exchange 2003 computer that contains the mailboxes so that out-of-office messages are only sent to the message sender if the recipient is explicitly named in the To or the Cc fields of the message. This new functionality is useful if your Exchange 2003 computer coexists with other mail systems that contain mailing lists that reside outside Exchange.

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk. To modify out-of-office message generation behavior, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. Expand the following registry key:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
3. Right-click ParametersSystem, point to New, and then click DWORD Value.
4. Type SuppressOOFsToDistributionLists, and then press ENTER to name the value.
5. Right-click SuppressOOFsToDistributionLists, and then click Modify.
6. In the Value data box, type 0x00000001, and then click OK.
7. Close Registry Editor.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

If a message is sent to a recipient, and the recipient is addressed only in the Bcc field, but not in a distribution list, and the recipient has turned on Out of Office Assistant, the recipient's mailbox store will still send an out-of-office message even though the SuppressOOFsToDistributionLists parameter is set. This limitation only applies if the recipient is addressed in the Bcc field, and the To and the Cc fields are blank. If there is at least one user in the To or Cc fields, then the registry parameter on the Exchange 2003 computer will suppress the recipient who was listed in the Bcc field from generating an out-of-office message.