There is no perfect answer to this question. The optimal frequency of publication in order not to push the Internet user to unsubscribe is once or twice a month.
Keep in mind that a hotel is not a newspaper or a magazine and that Internet users who have subscribed to your newsletter do not expect to receive constant news from you.
Communicate when you really have something to say. Send a loyalty offer in which the recipient has already stayed or the celebration of the customer's birthday, for example.
It is important to note that several studies indicate that the best time to send your emailing is between 10 and 11 am, a little bit before eating. (source: coschedule).