Ask HN: My responsibilities if I receive another company's emails (domains)?

I'm wondering what issues there are if any if I am receiving emails in error that are addressed to different companies because of similar domains.

This is actually an issue with 2 companies of fairly large size. It's like so:

  name@domainfizz.com (mine) > name@domainfizz.co.uk (others)
  name@domainbuzz.com (mine) > name@thedomainbuzz.com (others)

Basically, because I maintain a Catch All for these domains I sometimes receive and open emails addressed to companies in error. The senders are just getting the emails wrong.

So, I'm getting things addressed to:

  the-company-attorney@domainfizz.com (should be going to the UK addr)
  hr-directory@domainbuzz.com (should be going to thedomainbuzz.com)

Basically, I'm wondering how this should be handled going forward.