Email Error Logs - What are they doing?

[raincat]

Hi there.  Could somebody please explain to me what the Email Error Logs inside the ACP are supposed to be doing?

Or more specifically, I thought if someone registered using an invalid email address, the error logs would let me know.  (I do actually already understand that I could set my board such that new members are required to validate their email addresses before doing anything else, but I have another reason I'd be interested in deleting registrations with invalid emails before they'd be auto-deleted that's probably too long and uninteresting for this post.)

But I registered a couple of times for my own board using email addresses on a couple of different domains that I'm absolutely positive are bogus and will bounce email "invalid recipient," thinking that would show up in the Email Error Logs, thus alerting me that registration was not completed using a valid email address (when/if that happens in the future "for real" with live users, I mean).  And I did that about an hour ago and waited around for a bit, thought there might be a time lag.

But it's still completely blank in there, "There are no results to display."  

What are the conditions or situations via which something will show up in there?  Or were errors already supposed to be in there, and this actually means I'm experiencing difficulty with my specific board?

For these intentionally fake registrations completed by me, they do show up in the Members list with a helpful "Member has not yet responded to registration validation email" warning.   So, at least there's that.  But I was hoping there was some area within the ACP that would let me know that the email address to which that registration email was sent actually bounced it, "user unknown," "invalid recipient," etc.

Any feedback appreciated, thanks!