Another way is to have a dkim tag that specify the header that
indicates the stream classification
Many ways to kill the same bird.
If there is a reason why people aren't able to use a d= domain per
stream, I wish someone would explain in simple terms that even a
dimwit like me can understand.
The only arguments I'm aware of is that hostile or incompetent DNS
managers refuse to install key records, which isn't a very good reason
to add cruft to a standard and "I want to do it some other way" which
is even worse.
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