BCC stands for Blind Carbon Copy. The BCC header in email is never created by the sender mail client because the message should not display that it was sent to anyone in the BCC field.
The way that BCC mail is routed is via the SMTP envelope information.
When a mail server passes a message that has a BCC address to a recipient mail server the BCC address is only passed during the SMTP session.
Therefore in the case of a domain that has a MX record pointing to an ISP’s mailserver the only information regarding the BCC address is passed when the sender mailserver passes the message to the ISP’s mailserver. The ISP then routes the message into the catchall mailbox it has for that domain name.
If you have DomainPOP enabled, MDaemon periodically checks this catchall mailbox for new mail and downloads it into MDaemon for processing.
In the case of a email message that has been BCC’d, MDaemon will not be able to find a valid local email address or account that it can route the email message into unless the ISP that holds the catchall mailbox has added a custom header that contains it.
If there is such a header, you can add it to Setup -> Server Settings -> DomainPOP -> Parsing -> “Parse these headers for email addresses” so the custom header the ISP has added containing the BCC email address value is also processed.
In cases where there is no custom header added by the ISP, MDaemon has no choice but to pass the message to the postmaster alias as a “No addresses survived parsing process!” failure.
The user responsible for handling postmaster emails would then need to ascertain which local user the message might have been intended for and forward it to them as applicable.
Please note: This is a limitation of using DomainPOP and we would always encourage the use of direct SMTP delivery to prevent such issues. This article explains how to switch from DomainPOP to direct SMTP delivery.