I think this could be slightly off-topic, but worth answering.

If your program is reading mails from "Sent Items" you can extract Bcc info like other fields (To & Cc)

In the second case where your program is reading mails from "reader's" end(i.e. the client has received the mail and you're trying to see who else the mail was sent to) You Can NOT get info. See the RFC 2821 for SMTP. The relevant part is quoted below.

7.2 "Blind" Copies.

Addresses that do not appear in the message headers may appear in the RCPT commands to an SMTP server for a number of reasons. The two most common involve the use of a mailing address as a "list exploder" (a single address that resolves into multiple addresses) and the appearance of "blind copies". Especially when more than one RCPT command is present, and in order to avoid defeating some of the purpose of these mechanisms, SMTP clients and servers SHOULD NOT copy the full set of RCPT command arguments into the headers, either as part of trace headers or as informational or private-extension headers. Since this rule is often violated in practice, and cannot be enforced, sending SMTP systems that are aware of "bcc" use MAY find it helpful to send each blind copy as a separate message transaction containing only a single RCPT command.

There is no inherent relationship between either "reverse" (from MAIL, SAML, etc., commands) or "forward" (RCPT) addresses in the SMTP transaction ("envelope") and the addresses in the headers. Receiving systems SHOULD NOT attempt to deduce such relationships and use them to alter the headers of the message for delivery. The popular "Apparently-to" header is a violation of this principle as well as a common source of unintended information disclosure and SHOULD NOT be used.

Connecting the servers also won't work as the Bcc is handled by the "Sending" server. You may get Bcc info, if the sending server is NOT sticking to the RFC.

--VC

In reply to Re: How to extract mail_ids from bcc field by atemon
in thread How to extract mail_ids from bcc field by jesuashok

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