Not unless the list-owner spoofs email ... which is probably a violation
of a law or AUP.

Alternatively, the list-owner could QUIET ADD the userid and then QUIET
SET NOMAIL.  Then give instructions to the user to do a

SET listname MAIL

Of course this is still kind of bogus, especially if the list-owner gets
the userid@node somewhat incorrect i.e., the mail gets deliver to the
intended recipient, who then can not generate email from that specific
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