Do not forget about the original To recipient when forwading emails through mailinglists
When a mailing list is forwarding emails, it replaces the To recipient with the list recipient. But if the original To user was not the mailing list itself, the original recipient is lost and list users won't see him in their copy of the email.
(and the random_user is lost..)
I propose you put the original To recipient to Cc first if necessary to avoid this situation.