"No public key, stopping the processing chain" on demo.bitmask.net

on leech, there's one mail not being processed, it's /var/mail/vmail/Maildir/new/1396527615.Vfe12I20ceeM910743.leech:

2014-04-04 11:41:51+0000 [-] Starting processing skipped mail...
2014-04-04 11:41:51+0000 [-] --------------------------------------------------
2014-04-04 11:41:51+0000 [-] Processing new mail at '/var/mail/vmail/Maildir/new/1396527615.Vfe12I20ceeM910743.leech'
2014-04-04 11:41:51+0000 [-] Mail owner: 3e784cb3cde252a7be0d1d67ef75b921
2014-04-04 11:41:51+0000 [-] Starting factory 
2014-04-04 11:41:51+0000 [HTTP11ClientProtocol,client] No public key, stopping the processing chain
2014-04-04 11:41:51+0000 [HTTP11ClientProtocol,client] ++++++++++++++++++++++++++++++++++++++++++++++++++
2014-04-04 11:41:51+0000 [HTTP11ClientProtocol,client] Done processing skipped mail
2014-04-04 11:41:51+0000 [HTTP11ClientProtocol,client] Stopping factory 

(from redmine: created on 2014-04-04, closed on 2014-04-16)