The jBPM 4 code doesn't know how to authorize you:
Caused by: com.sun.mail.smtp.SMTPSendFailedException: 553 You are not authorized to send mail, authentication is required
I'm pretty sure this is a bug in the jBPM 4.4 code -- I fixed the same issue in the jBPM 3 and jBPM 5 codebase:
See JBPM-3386 for jBPM 3 and JBPM-3032 for jBPM 5.
Unfortunately, I don't do anything with the jBPM 4 code.. My apologies!