Exchange Server Connector for POP3 Mailboxes deliver multiple copies of messages (264249)

SUMMARY

When both the following conditions are true:

Messages are being downloaded from a global Post Office Protocol 3 (POP3) account (global POP3 accounts are also known as "multiple recipient accounts" or "domain accounts"). This behavior does not occur when you configure individual user mailboxes to use the POP3 connector.
The global POP3 mail host has separated the original message into multiple individual messages.

On a server that is running Microsoft BackOffice Small Business Server 4.5, Microsoft Small Business Server 2000, or Microsoft Windows Small Business Server 2003, the Connector for POP3 Mailboxes may deliver multiple copies of an e-mail message to the recipients.

MORE INFORMATION

When an individual message is sent to multiple recipients that are specified in the To, Cc, or Bcc boxes of a Simple Mail Transfer Protocol (SMTP) message, some global POP3 mail hosts create a separate message for each recipient. The global POP3 host that receives the message reads the message header, compares the recipient's addresses with an internal routing table or alias table, and then places the e-mail messages in a single mailbox. The new messages still retain the original message ID, as well as the information that is in the To and Cc boxes. When the Connector for POP3 Mailboxes downloads the messages from the POP3 server, and then transfers the messages to Microsoft Exchange Internet Mail Service (IMS) or the Microsoft Exchange SMTP virtual server without modifying the message. The Exchange Server-based computer then delivers each message to the accounts that are specified in the header.

Multiple messages may be sent to users in cases where multiple recipients on the same Exchange Server-based computer are specified in the header of the message. For example, if a message is sent to user1@microsoft.com, with user2@microsoft.com specified in the Cc box of the message, user1 and user2 both receive two copies of the message because the POP3 connector downloads two copies of the same message from the global POP3 mailbox. Messages that are addressed to recipients in the Bcc box may or may not be delivered, depending on the configuration of the sending mail host.

For additional information, click the following article number about POP3 connector support for Bcc recipients to view the article about POP3 connector support for Bcc recipients in the Microsoft Knowledge Base:

265739 Microsoft Exchange Connector for PO265739 Mailboxes does not support Bcc

This behavior does not occur in cases where the host for the POP3 global mailbox parses the incoming SMTP message for multiple recipients in the same e-mail domain and does not create individual messages for each recipient. In this case, because only a single message is delivered to the POP3 connector, each recipient receives only a single message. This behavior does not occur in cases where the host for the POP3 global mailbox parses the incoming SMTP message for multiple recipients in the same e-mail domain and does not create individual messages for each recipient. In this case, because only a single message is delivered to the POP3 connector, each recipient receives only a single message. This behavior can be resolved if the POP3 mail host's operator (typically an Internet Service Provider (ISP)) configures the POP3 mail host to deliver only a single message to the global mail account mailbox, which is used by the POP3 Connector, instead of creating multiple instances of messages which contain a Cc or a Bcc (or both) address line.