La respuesta fue:
550 Requested action not taken: mailbox unavailable


Final-Recipient: rfc822; olga@ingesist.com
Action: failed
Status: 5.0.0
Remote-MTA: dns; mx00.1and1.es. (212.227.15.41, the server for the domain ingesist.com.)
Diagnostic-Code: smtp; 550 Requested action not taken: mailbox unavailable
Last-Attempt-Date: Mon, 24 Jul 2017 09:05:42 -0700 (PDT)