So, unmunged in original mail, displays on web GUI:
munged: postmaster(a)[127.0.0.1] postmaster(a)example.com unmunged: postmaster@localhost @example.com @localhost postmaster@localhost
And in the arhive itself ugh, slightly worse, but not even the same set!:
munged: <postmaster(a)localhost> postmaster(a)example.com postmaster(a)localhost unmunged: @example.com @localhost postmaster@[127.0.0.1]
In any case, that applies to body, headers in archive aren't @ (a) munged.