Email going to a user at a similar domain name

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http://serverfault.com – I guess this is more of a best practice/policy question. I'm the postmaster for example.net. Another company has example.com. I get the catch-all emails, any email that doesn't have a user account on my server. What should I do, if anything, if emails keep coming to [email protected] when it should be going to [email protected]? Should I just setup a forward, alert the user or ignore it? (HowTos)