It disables/enables the repeated prompts to warn that you are trying sending a private reply to a message which arrived via a mailing list, but the list sets a Reply-To: header which redirects your reply back to the list
Honek errepikatutako galdera gaitzen/desgaitzen du, posta-zerrenda bidez jasotako mezu bati erantzun pribatu bat (baina zerrendak ezarritako 'Erantzun honi' goiburuak zerrendari erantzutera bideratzen zaituena) bidaltzen saiatzen ari zarela abisatuz.