diff --git a/ChangeLog b/ChangeLog
index 1500766..8851f28 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,7 @@ yapfaq 1.1.0 (unreleased)
   * --test: Force -o if -n is not set.
   * Add conversion script for old status files.
   * Accept a posting-frequency of "never", too.
+  * Check for illegal headers and stop posting, if found.
 
 yapfaq 1.0.1 (2025-01-24)
   * Add %t placeholder for Message-ID (feature parity with 0.9).
diff --git a/bin/yapfaq.pl b/bin/yapfaq.pl
index eebe9b7..11494cc 100755
--- a/bin/yapfaq.pl
+++ b/bin/yapfaq.pl
@@ -412,6 +412,17 @@ sub BuildPosting {
     return '';
   }
 
+  # check for illegal headers
+  my $FoundIllegalHeader = 0;
+  foreach (qw/Date User-Agent X-Newsreader X-Mailer Injection-Date
+    Injection-Info NNTP-Posting-Date NNTP-Posting-Host X-Trace/) {
+    if ($Header{lc($_)})  {
+      warn "W: $_ header may not be set in '$HeaderFile'.\n";
+      $FoundIllegalHeader = 1;
+    }
+  }
+  return '' if $FoundIllegalHeader;
+
   # add Date:
   push @Headers, 'Date: ' . $TD->strftime('%a, %d %b %Y %H:%M:%S %z') . "\n";
   # add missing Message-ID: