postfix header checks

content/blog/_index.md

@@ -1,6 +1,7 @@
 +++
 draft = false
 title = 'Blog'
+framed = true
 
 [params]
   Toc = false

content/blog/mail_server_alpine_postfix_dovecot_tutorial/index.md

@@ -386,6 +386,25 @@ mailbox_size_limit = 0
 
 By default, `mailbox_size_limit` is `51200000`. This number is in bytes. You can similarly set a `message_size_limit`.
 
+Let's hide some sensitive info that tends to get attached to email headers by clients. Edit
+`/etc/postfix/header_checks`, or create it if it doesn't already exist, and add the following lines:
+
+```plaintext
+/^Received: .*/            IGNORE
+/^User-Agent: .*/          IGNORE
+/^X-Originating-IP: .*/    IGNORE
+/^X-Mailer: .*/            IGNORE
+/^Mime-Version: .*/        IGNORE
+```
+
+Now add the following to your `/etc/postfix/main.cf`:
+
+```conf
+header_checks = regexp:/etc/postfix/header_checks
+smtp_header_checks = $header_checks
+mime_header_checks = $header_checks
+```
+
 Finally, here are some various hardening settings you can add to your `/etc/postfix/main.conf`:
 
 ```conf

hugo.toml

@@ -67,7 +67,6 @@ theme = 'terminal'
   # can be overridden in a page's front-matter
   # TocTitle = "Table of Contents" # default
 
-
 [params.twitter]
   # set Twitter handles for Twitter cards
   # see https://developer.twitter.com/en/docs/tweets/optimize-with-cards/guides/getting-started#card-and-content-attribution