Out of office replies from bulk emails

Out of office replies from bulk emails

When I send bulk emails through Bigin, i.e. one email to multiple contacts, I expect to receive some automatic replies, for instance out of office replies. It would be very unusual if I didn't. However, I'm unable to find these automatic replies anywhere. They're not in my notifications and I can't find them when I do a search within contacts for the usual key words. Where do they go please?