It depends on the type of business. Our studies have revealed Tuesday and Wednesday as the best days, and either 9:00 – 10:00 in the morning or around 2:00 in the afternoon as the best times. Of course, the only way to really know what works best for your audience is to experiment.  Brevo’s Premium plan offers a Send Time Optimization functionality, which uses machine learning to send emails at the best time for each individual recipient. Well worth checking out if you’re a high volume sender with subscribers in different time zones.