Simple answer; You can't.
However, you could always 1) make your ISP not block nobody@-address, or 2) make them run a separate apache for you, running under your uid.
The above might not be solvable, so you can try adding additional headers, such as Reply-to and Errors-to. Not all mail-servers bounce to Errors-to, but it's better than nothing, isn't it? :-)