Rewrite "from" for specific "to" addresses

Postfix 2.1 and above supports conditional operators within regex and pcre tables. In your case second_header_checks using these conditionals should look like this:

if !/^From:(.*)@verified-domain.com/i
/^From:(.*)/i REPLACE From: <[email protected]>
endif

You can test your lookup tables without actually sending anything like this:

peter@mail:~peter $ cat msgheaders
From: <[email protected]>
To: [email protected]

peter@mail:~peter $ postmap -hmq - regexp:/etc/postfix/second_header_checks < msgheaders
From: <[email protected]>     REPLACE From: <[email protected]>

peter@mail:~peter $ cat msgheaders-1
From: <[email protected]>
To: [email protected]

peter@mail:~peter $ postmap -hmq - regexp:/etc/postfix/second_header_checks < msgheaders-1
peter@mail:~peter $