That's not what .lock files protect against. They protect against
simultaneous write of the mailbox by the MTA (e.g. sendmail calling
/bin/mail) and the MUA (e.g. imapd). The corruption that would happen is
if, while imapd is updating the INOBX, a new message is delivered.
The UW imapd protection that you're talking about only protects against
multiple imapds, and that only works when the file is local (not NFS
-- Mark --
Science does not emerge from voting, party politics, or public debate.
Si vis pacem, para bellum.