procmail file locking

Can anybody tell me what file locking formail /procmail uses
I am using it with sendmail / pine on linux (Redhat) and i am getting 
random corruption in my folders ??

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#include <StdDisclaimer.h>            |  Alban Pearce 
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alban(_at_)scot1(_dot_)ucsalf(_dot_)ac(_dot_)uk
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