[Dovecot] plugin problem

I'm trying to do a rewrite of the dspam_plugin for dovecot 1.1b1. There are some API changes that warranted an update of the plugin. Also, I wanted the dspam_plugin to be able to handle pristine mails for dspam retraining, as opposed to the signature based retraining.

Question: How can I retrieve the full unix path for a specific mail?

The original code uses mail_get_first_header() to retrieve the signature header. I need something like mail_get_mail_file_path(&path) which I then could pass on to dspam. Is there some such function available?

Thanks in advance /Lars