Disadvantages BCC messages are not routed with your organization. If users subscribe to a mailing list, and the ISP mail server does not support the 'for' clause, messages from some mailing lists will not be routed. Why is this? When mail is sent via SMTP, the actual recipient is provided by the sender on the "RCPT" command. This information is called part of the "envelope" (since it is outside of the message), and is sometimes not included anywhere in the actual mail message's header. For a single recipient, this is not a problem. If the mail is in your mailbox, you know it is for you. However, if all mail directed at a specific domain goes into the same mailbox, there may be no way of determining who the mail should be delivered to. This is most often the case for messages from mailing lists or if the BCC: field was used. There is however a solution for this problem. The most common is in the Received: line. According to page 32 of RFC 821, the Received: line should look something like this: Received: from sender.com by yourisp.com for you@yourdomain.com The "for" clause is derived directly from the envelope information, so even if the To: and Cc: lines make no mention of "you@yourdomain.com", the true recipient can be found here. Thus, any POP to Exchange solution must (at least) be able to parse the Received: lines in the header in order to forward the mail to the correct local recipient. Note: An easy way around the above problem is to create dedicated POP3 mailboxes for lists. Then route the lists to a public mailbox, so that other users can also benefit from the lists.