On 24/04/25 10:18, Peter Moylan wrote:

The big problem, I suspect, is that some big mail services might be
adopting a "silently reject" policy, simply discarding mail they
don't like instead of returning a failure reply. My choir uses a
Yahoo mail account (against my advice), and a problem we had was
that messages to all members went only to some members, and we were
never notified about the failures. I'm no longer on the choir
organising committee, so I don't know whether they are still doing
it.

You might be asking "why were there delivery failures?". In that case it
was because Yahoo mail was (and possibly still is) a major source of
spam, so it was often blacklisted. Because of this, Yahoo adopted a
policy of not telling senders when their mail wasn't deiivered.

The 2rosenthals server is not blacklisted, but it could be on someone's
private blacklist.