- it actually *is* an expected condition that a to_net.addr or from_net.addr
msg header field is populated with a valid address (string) even though the
to_net.type or from_net.type value is NET_NONE.

The nntpservice.js and newslink.js modules rely on this behavior to display
and export local NNTP-posters' email addresses in message headers, but still be
able to identify newslink-imported messages as *not* local (the from_net.type =
NET_INTERNET) and thus not export them back to the network.

This was not the original intention behind these header fields in SMB, but it
was retrofitted to support this condition 10+ years ago and I forgot.