Hi Iuri,
The from_party_id and to_party_id are args of another callback (acs_mail_lite::complex_send) that was available in 5.4 but has been removed in 5.5.
Anyhow, the implementation in mail-tracking is not correct since it's for the acs_mail_lite::send callback which declares the following args:
ad_proc -public -callback acs_mail_lite::send {
-package_id:required
-message_id:required
-from_addr:required
-to_addr:required
-body:required
{-mime_type "text/plain"}
{-subject}
{-cc_addr}
{-bcc_addr}
{-file_ids}
{-object_id}
}
The implementation must use the same signature. In other words, it's the implementation that need to be fixed, not the callback declaration in acs-mail-lite.
Hope that will help.