The only possible thing I can see in the logs for the admin@BogoLinux.net entry might have been an attempt to read e-mail on NS for user admin via the POP3 Proxy:
The email@example.com box contains e-mails from @stephdl's ddclient.
The admin (no domain) box was the one created at NS install.
Here's what NS thinks exist:
On a slightly related note. Is there any way to set up a shared e-mail box so that a single remote client can download both root's and admin's mails. As noted, NS6 sent everything to admin. NS7 appears to send (most) to root.