From: Wietse Venema on
Wietse:
> Postfix does not log message changes unless you turn on debug
> logging. Message changes can be quite extensive, such as deleting
> a header, adding a header, or replacing the message body. Such
> logging is not of interest for production usage.

Jesus Cea:
> I find it VERY useful for production use. Could you consider a
> configuration option for a future postfix version?.

I don't know how Postfix would log:

- delete header (log the old header text?)
- change header (log old text AND nex text?)
- replace body (log old text AND new text?)

For now, you can use milter_header_checks to log all headers that
are added by a Milter application.

/etc/postfix/main.cf:
milter_header_checks = pcre:/etc/postfix/milter_header_checks

/etc/postfix/milter_header_checks:
/(.+)/ WARN $1

The downside is that this is logged as a warning; I suppose that
it would make sense to add a new INFO action to Postfix that logs
the text with "normal" priority.

Wietse