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I need to modify the "From:" header line in incoming e-mail messages only if "Message-Id:" starts with a defined string. So in main.cf I put:

header_checks = pcre:/etc/postfix/header_checks

and header_checks file contains:

if /^Message-Id: <footext.+/
/^From: (.*)@johndoe.com/ REPLACE From: ${1}@ext.johndoe.com
endif

It doesn't work, the condition does not take. What am I missing?

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2 Answers 2

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http://www.postfix.org/header_checks.5.html

if /pattern/flags

   endif  Match the input string against the patterns between
          if  and endif, if and only if ----> the same <----- input string
          also matches /pattern/. 

you can not use an if/endif block to match a different header.

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  • So it seems header_checks is no good to my needs, isn't it? Can you suggest a way to have a conditional replace among header fields (matching a different header line)? Thanks in advance for any help you will offer.
    – Gabriele
    Apr 14, 2013 at 7:11
  • I'm not sure there is a simple way to do this with postfix internal features. For this kind of stuff, I usually attach a content filter like FuGlu (disclaimer: written by me)
    – Gryphius
    Apr 15, 2013 at 7:43
  • Couldn't find the quote in the link anymore. So it seems this syntax would work in the newer versions of postfix?!?
    – t7tran
    Jun 4, 2020 at 6:07
  • No, the restriction is the same like before, things have only been rephrased: [...]then match **that input string** against the patterns between if and endif. Oct 12, 2021 at 15:42
  • There's an additional section in the docs making that clear as well: Many people overlook the main limitations of header and body_checks rules. These rules operate on one logical message header or one body line at a time. A decision made for one line is not carried over to the next line. Oct 12, 2021 at 15:58
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I came across this post and thought to update since I had a similar issue: I took a different approach using postfix pipe as suggested in some of these resources:

and just because I ran into the issue of loops:

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