Dave CROCKER wrote:
Might as well ask an even more basic question:
I had the impression that multi-recipient RCPT-TO usage had
essentially disappeared. The growth of sending per-recipient tailored
messages seemed to be the cause.
Wow. Not in my experience, definitely not for ordinary B-to-B, where the
median is probably over 1.5, and not even for legit bulk.
I had a particularly memorable sender a year ago that sent newsletters.
They highly optimized their RCPT TO's, so not only would they send to
multiple recipients in the same message, they'd combine recipients in
different domains if the MX's allowed it. It was a headache for me
because some of my customers were careless with their MX records, and
mail would be combined for recipients that were on different mailhosts.
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