[Exim] Lock file

Just a quickie,

Looked in the docs and found nothing (could just be me), I need to tell if a
mail message is locked, I assumed the pressence of a "-P" file in the spool
directory denoted a state of lockedness, but having removed this file for
one mail it still seemed to be locked (If you're bored, could you tell me
what the -D and -H files are, I suspect what they are, but would like
confirmation)

CHEERS,

Zed