Insert custom header in Mail logger plugin

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

-- Att. Bruno Galindro da Costa