[exim] Exim 4.72: preventing backscatter

Hello,

Could someone suggest better way to prevent Exim backscatter? Exim 4.72
is in use. There are two solutions considered:

1. Set up proper ACL to prevent backscatter (verifying the sender before
doing so)
2. Create 'catchall' router, intercepting all unrouteable addresses (I
think this is better solution).

I couldn't find solutions (configuration snippets) within reasonable
timeframe. Could someone direct me to some?

If I need to provide Exim configuration file, please let me know what
parts I may omit/mangle prior to sending here.

Thank you.

Sincerely,
Konstantin