Strange- my email was missing the @yahoo.com in my settings here on the site Xenforo, I haven't been recieving any mailing on threads I was watching etc. How is that possible? I have never even went into my setting until today to correct the email.
You would need to view your server's raw mail delivery logs (requires root access, generally). By default, XenForo simply hands the mail to a local MTA which is then responsible for delivering, retrying, etc.