that seems to cover it. If smtp_generic_maps isn't working for you, perhaps read that section again, since it seem to do exactly what you want
> smtp_generic_maps = hash:/etc/postfix/generic
> [hidden email][hidden email] > [hidden email][hidden email] > @localdomain.local [hidden email] >
> When mail is sent to a remote host via SMTP, this replaces [hidden email] by his ISP mail address, replaces [hidden email] by her ISP mail address, and replaces other local addresses by his ISP account, with an address extension of +local (this example assumes that the ISP supports "+" style address extensions).
'The gods,' he said. 'Imprisoned in a thought. And perhaps they were
never more than a dream.' --Sourcery