Insert custom header in Mail logger plugin

[Bruno Galindro da Costa]

Is it possible to log a message custom header through Mail logger plugin or
other method? It seems that there are a fixed number of info that is
configurable via mail_log_fields (http://wiki2.dovecot.org/Plugins/MailLog).
..

My custom header is X-VERTICAL-IP-Quarantine-ID and I want a log event like
this one:

Aug 27 09:48:13 imap dovecot: imap(user at domain): copy from INBOX: box=SPAM,
uid=213, *X-VERTICAL-IP-Quarantine-ID=u7cnUqYDPA9a*, msgid=<
0.0.D7.290.1CFC155CE887302.0 at etm2.com>, size=26481, vsize=26949,
from==?UTF-8?Q?Dafiti=20-=20Parceiros?= <aaa at domain>,
subject==?UTF-8?Q?Sapatos=20com=2040%OFF?==?UTF-8?Q?!=20Apro?=?
=?UTF-8?Q?veite!?=

-- 
Att.
Bruno Galindro da Costa