I know that this may be a silly question but have you checked your junk mailbox? I had a similar experience with new members last year. They kept on telling me that no email had been received. When some brought their devices in I soon found the missing emails. For some reason, all the emails inviting new members had ended up amongst their "junk mail". Just had to mark the emails from voice as being safe, so that further emails don't go a similar way (e.g. when you use the blog, noticeboard or send out a general email to the group) .
From time to time it still happens to me that the odd voice email ends up in the junk pile!
All the best