I think hes talking about when you go offline (I'm not positive that its when your offline, but thats what it seems like) and people keep talking to you, it sometimes sends you e-mails of each message that they send.
This is really annoying, I came on with 200+ e-mails today of people ranting while I was offline. Theres no way to turn it off either (and if there is, no one I know can find it).
If its not what he was talking about, then whoops