OT: Exim rewriting

[sysadm]

Dear all
I am tired of people sending mails not following the (RFC-2822) Some 
companies does not ad the DATE: header in their newsletters/mails. 
However I cannot just delete those mails. I have tried to contact those 
companies without any luck. I have decided to ad the DATE header in my 
MTA (exim), if it does not exist already, but how do I do that ?

OS: CentOS 4.3
MTA: Exim 4.43


Regards jg