original date

Hallo 

i use procmail, fetchmail, postfix and courier-imap
fetchmail get my mail from my pop briefcases from my isp periodically ( 2 
minutes)
But if i kill fetchmail and reactivate him par exemple after 3 hours, all Mails 
have the same date
i readed that i must remove with procmail the last receive-header to get the 
original date back
can anybody tell me how ? 

thx  Frank