Rewrite from-address of all outgoing e-mail from a server using Postfix

I want postfix to rewrite the from address of all this server's outgoing e-mail. Anyone know how could I accomplish this?

This is described in http://www.postfix.org/ADDRESS_REWRITING_README.html#generic

It states to use the smtp_generic_maps to rewrite the outgoing addresses (in header and envelope!). The example given there uses the hash lookup table for rewriting. But you are - as usual in Postfix - able to use the regex or pcre lookup table for rewriting. Which could rewrite like

/.*/    [email protected]

This approach even enables you to rewrite addresses only under some special conditions that you can write as regular expressions.