Developers of Sympa

[<address@concealed>]

I know this is not possible yet according to the following:
http://www.sympa.org/faq/tips_and_howto#how_to_customize_each_message_for_each_subscriber

Regardless I need to do this with my installation of Sympa (5.2.3). Has anyone
done this yet or can anyone point me in the right direction on where to begin
like what program(s) that will need to be updated to do so?  

I was thinking maybe mail.pm would be the program to patch but if anyone has
already done this it would be great if you could share the code with me or let
me know of anything tricky to updating Sympa to do this.

Thanks!
Jason