- fixed logic flaw in email header manipulation to calculate the nilsimsa digest.
The regular expressions acted on the whole header.  Not entirely sure how it worked so well for so long!
Used email module's parsing ability to correct.  Should provide much more accurate results
- the lock file algorythm used just didn't work I noted when the mail server was under
attack by a botnet

todo:  move code out of main, use standard module for lock file
cleanup - too lazy to rebase :)