Peter Schultze <petersch@cs.ucla.edu> writes:
Sending a message in Rmail to a local address always triggers a warning
"Email address localuser looks invalid; send anyway? (y or n)".
from lisp/gnus/message.el
This only occurs in V. 27.1, but not in V. 26.3.
This is not useful on systems where the MTA is configured
to handle local addresses.
This could be related to bug#23054
You should be able to shut this off by pushing '(bogus-recipient .
disabled) to `message-syntax-checks'. See the "News Headers" section of
the Message info manual.
HTH,