How to create a black hole email address?

I would like to create a black hole email address. Can you do that with LiveConfig? How?

If I would follow these instructions would LiveConfig accept a redirection to devnull ?

Two use cases:

• The typical emails automatic notification emails with no-reply@emailaddress.com. Probabably will have a reply-to header, but some user can still start using it and I just don't want to clean out the mailbox
• A billing software like WHMCS can only associate clients with email addresses. Some clients just don't want to receive emails or don't want to give an email address. I create a unique email for them, because WHMCS cannot do without, but I don't want to see emails nor see them bounce.

Both make sense to me and while they might be illegal in the strict sense, nobody is really bothered by this use.

Meanwhile I found a way to create a blackhole address:

• Add this line to /etc/aliases:
  
  
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  null: /dev/null

  
  

• Compile the changes by running:
  
  
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  newaliases

  
  

• Make a custom virtual alias file /etc/postfixt/virtual_alias_custom with:
  
  
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  null@existingmaildomain.com  null@localhost

  
  

• Take care that the file permission and owner are the same as /etc/postfix/virtual_alias and then run in the /etc/postfix directory:
  
  
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  postmap virtual_alias_custom

  
  virtual_alias_custom.db should appear now.
  

• Modify /etc/postfixt/main.cf to include this new file:
  
  
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  virtual_alias_maps = hash:/etc/postfix/virtual_alias hash:/etc/postfix/virtual_alias_custom

  
  

• Restart Postfix