Re: puzzling junk mail
On 2/8/2019, 12:34:31 AM, Daniel <dxmm@xxxxxxxxxxxxxxxxxxxxx> wrote:
as some servers do apparently require a To: addressee,
Never seen one that did.
SMTP doesn't distinguish To Cc or Bcc, only RCPT-TO.
SMTP doesn't, but some servers (e.g. filtering tools used by the
server's Mail Transport Agent) may reject messages that don't have To:
or cc: addresses. That's a decision that's made, based on content
scanning of the message content.
I know that there are also some servers that may reject (or at least
tempfail) envelopes with more than a specified number of addresses in
the envelope. Last I recall, Yahoo's threshold was 10 addresses.
I know of a longtime spam operation that uses addresses harvested from
victims, where they send to portions of the victim's address book, and
where all the addresses are To: (and display names shown in alphabetic
order). For this, one of the hooks is that addressees are likely to be
known to each other (as well as to the name associated with the forged
sender address). One of the trademarks of this operation is that content
always goes out in increments of about 10 at a time (give or take), and
my assumption has always been that the relatively short distribution
list is done as a way of getting stuff past servers that limit the
number of addresses in an envelope.
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