On Fri, 13 Apr 2001 11:17:58 -0500, Paul Russell <[log in to unmask]> wrote:

>The term "BCC" is commonly used by user support staff
>to explain the presence of envelope-recipient addresses which do not
>appear on the 'To:' line, because while most email users understand
>the term "BCC", most are not be familiar with the intricacies of SMTP.
>Nor should they need to be.

If you read RFC821 carefully, you will find that the MTA (Mail Transfer Agent)
deals only with  MAIL FROM:<return_address> and RCPT TO:<recipient_address>.
The MTA is, infact, not allowed to look into the DATA section where the (RFC822)
To: line you will actually see in your email may be found.

The favorite analogy is postal mail.  On the outside of your envelope is a TO:
and FROM:.  In attempting delivery, the Post Office is only allowed to look at
these 2 addresses.  It is not allowed to look inside the (sealed) envelope for
anything else (other To: addresses, cc:, or Bcc:, etc) that might be there.

The difference with e-mail is that multiple RCPT TO:<recipient_address> can be
and infact should be specified in the outside of the 'envelope'.  Inside the
envelope is 1 copy of the list message and its (RFC822) To: line will say
To: [log in to unmask]  so infact the (RFC822) To: will not match any of the
(RFC821) RCPT TO:.  Some mail (usually corporate) mail systems perform this test
and reject mail unless the (RFC821) RCPT TO:<address> matches the (RFC822) To:
address AND the address is looked up and verified to exist.  Thus some people in
some corporate mail systems cannot receive mail from a LISTSERV list.

Where "too many bcc's" could be applicable is what Webtv.net/webtv.com have
recently instituted.  If there are more than 20 (RFC821)

RCPT TO:<[log in to unmask]>
RCPT TO:<[log in to unmask]>
RCPT TO:<[log in to unmask]>
...
RCPT TO:<[log in to unmask]>

then (mail server log excerpt)
...
04:13:12 mailsorter-102.bryant.WEBTV.NET( 15) >>> 250 Ok
04:13:12 mailsorter-102.bryant.WEBTV.NET( 15) >>> 250 Ok
04:13:12 mailsorter-102.bryant.WEBTV.NET( 15) >>> 250 Ok
04:13:12 mailsorter-102.bryant.WEBTV.NET( 15) >>> 452 Error: too many recipients
04:13:13 mailsorter-102.bryant.WEBTV.NET( 15) >>> 452 Error: too many recipients
04:13:14 mailsorter-102.bryant.WEBTV.NET( 15) >>> 452 Error: too many recipients
04:13:29 mailsorter-102.bryant.WEBTV.NET( 15) >>> 421 Error: too many errors
04:13:29 ( 15)O closed WEBTV.NET mailsorter-102.bryant.WEBTV.NET,  WSAECONNRESET

Then Webtv aborts the entire transaction and refuses to accept any mail.  AOL
may be preparing to (or doing) the same thing.  Obviously this has negative
implications for large lists with many subscribers at AOL.com addresses.