Save as `data/conf/postfix/mailcow_anonymize_headers.pcre`: ``` /^\s*Received:[^\)]+\)\s+\(Authenticated sender:(.+)/ REPLACE Received: from localhost (localhost [127.0.0.1]) (Authenticated sender:$1 /^\s*User-Agent/ IGNORE /^\s*X-Enigmail/ IGNORE /^\s*X-Mailer/ IGNORE /^\s*X-Originating-IP/ IGNORE /^\s*X-Forward/ IGNORE ``` Add this to `data/conf/postfix/main.cf`: ``` smtp_header_checks = pcre:/opt/postfix/conf/mailcow_anonymize_headers.pcre ```