renaming a .local domain to .com for every relayed message

Situation: about 10 virtual machines (linux) that run postfix to send e-mails for several users. Those e-mails are all relayed through a central server which then sends them to the internet. The virtual machines have names like: redmine.vanheusden.local or scm.vanheusden.local and so on. I would like the central postfix server to rename *@vanheusden.local to @vanheusden.com…