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Microsoft Exchange Connector for POP3 Mailboxes does not support Bcc
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Messages that are delivered to a global POP3 account with a recipient specified in the Bcc box may not be delivered to the intended recipient and neither a non-delivery receipt (NDR) or an error message are generated.
Note that this behavior does not occur with standard, single-user POP3 mailboxes.
This behavior is by design. The Microsoft Exchange Server Connector for Post Office Protocol 3 (POP3) mailboxes do not support delivery of messages to recipients that are specified in the Bcc box of an e-mail message.
On a server that is running Microsoft Small Business Server 2000, you can work around this behavior by configuring a single-user POP3 account in the Connector for POP3 Mailboxes instead of a global POP3 account. When you are using a single-user account, the Connector for POP3 Mailboxes delivers all the mail from the POP3 mailbox to a single Exchange mailbox. Therefore, it is not important whether the recipient's e-mail address appears on a downloaded e-mail message.
On a server that is running Microsoft Windows Small Business Server 2003, you can work around this behavior by configuring the POP3 Connector to send all undeliverable e-mail that the connector downloads to a specific Exchange mailbox. To specify a mailbox for undeliverable e-mail messages in the POP3 Connector, follow these steps:
Click Start, point to All Programs, point to Microsoft Exchange, and then click System Manager.
In Exchange System Manager, expand Connectors, right-click POP3 Connector Manager, and then click Properties.
Click the Troubleshooting tab, click an Exchange mailbox in the box under Undeliverable POP3 Mail, and then click OK.
This behavior occurs due to a limitation in POP3. When an Simple Mail Transfer Protocol (SMTP) message is delivered to a mail host, the mail host is responsible for routing the message to the intended recipients. During normal operation, the mail host constructs the message without the Bcc box in the e-mail message. The message is then delivered to a global POP3 account. When the POP3 connector downloads the message, the recipients are not visible in the message, just as they would not be visible to a standard POP3 client that downloads the same message. The POP3 connector delivers the message to Microsoft Exchange Internet Mail Service (IMS) unchanged. The IMS is unable to forward the message to the intended recipient because the header of the message does not contain the original reference to the Bcc recipient.
Recipients that are specified in both the To and Cc boxes of the same message do receive the message.