When VPOP3 is configured to download mail from a shared (catch-all) POP3 mailbox at your ISP, it has to read through the standard message header lines to see who the message is for. It looks at the To, Cc, Received, Apparently-To, Resent-To and Resent-Cc header fields for a recipient it recognises.

In most cases this will work fine. However, if the message has been BCCd to you, the recipient address will not be in the message header at all (that is the whole point of BCCd mail). The message reaches your ISP mailbox because the actual recipient is listed in the SMTP Envelope but most ISPs will throw that information away when they deliver the message into a POP3 mailbox. Because of this there is no automatic way that VPOP3 can work out the message's recipient(s). Instead it will deliver the message to the failed recipient address specified in the Mail Collector → Routing Errors settings in VPOP3.

Some ISP will copy the SMTP Envelope recipient information into custom header fields in the message, such as X-RCPT-TO or Delivered-To. In this case, you can tell VPOP3 to use this header information.

If your ISP does not copy the SMTP Envelope information into the header your options are limited:

• Manually. An aIncomdministrator can go through the messages which were not delivered, and forward them to the appropriate person.
• Mappings. Many BCCd messages are actually from mailing lists. In this case the To header will often have the address of the mailing list in it. In this case you can create a Mapping of type POP3 from the mailing list address to the user(s) who want to receive the message.
• SMTP Feed. If you can switch to an incoming SMTP Feed for your mail (instead of POP3 collection), then that will allow the SMTP Envelope information to be given directly to VPOP3, so the problem will vanish.

If your ISP adds custom header information, then, to tell VPOP3 about this, go to Mail Collectors → POP3 Routing → Configure Routing Options in the VPOP3 settings. In the Special Header Fields box put information defining the header field(s) which you want VPOP3 to look at. Some examples are:

• Delivered-To: - Finds user@domain.com in Delivered-To: user@domain.com
• X-RCPT-To: * - Finds user@domain.com in X-RCPT-To: user@domain.com (equivalent to the above one)
• Delivered-To: 547-* - Finds user@domain.com in Delivered-To: 547-user@domain.com (specifies an explicit prefix)
• Delivered-To: 547-* confirmed - Finds user@domain.com in Delivered-To: 547-user@domain.com confirmed (specifies an explicit prefix & suffix)
• Delivered-To: 547-* ~ - Finds user@domain.com in Delivered-To: 547-user@domain.com random text (specifies an explicit prefix and random suffix)