I have sever clients who will get more than one email e.g. [email address removed] as well as [email address removed] 

If any of the email addresses have changed and no longer are active e.g. jsmith no longer works at acme, you get the generic message saying qb is unable to send emails due to a network connection failure which sounds more like QB can't even ping 8.8.8.8 let alone send emails to anyone in the world.