What little details we had to go on have been removed from the question. Please review Asking Better Questions and add the details on what you’re looking to achieve and what you’ve tried so far.

Out-of-office (OOF) can be set via Outlook or OWA but replies to external senders depend on setting one for internal user. A transport rule can be used to disable delivery of OOF autoreplies to internal users as outlined by Ivan, which I thought answered this question quite well but then the related details were removed from the question.