sending mail from Android with K9 fails

Hello,

I have seen this error in the james-server.log when trying to send email 
from my K9 Mail client in Android.

ERROR 00:26:22,594 | org.apache.james.imap.processor.StatusProcessor | 
Status failed for mailbox 
#private:[email protected]:K9MAIL_INTERNAL_OUTBOX
org.apache.james.mailbox.exception.MailboxNotFoundException: 
#private:[email protected]:K9MAIL_INTERNAL_OUTBOX can not be found
         at 
org.apache.james.mailbox.jpa.mail.JPAMailboxMapper.findMailboxByPath(JPAMailboxMapper.java:143)
         at 
org.apache.james.mailbox.store.StoreMailboxManager.getMailbox(StoreMailboxManager.java:276)
         at 
org.apache.james.imap.processor.StatusProcessor.doProcess(StatusProcessor.java:63)
         at 
org.apache.james.imap.processor.StatusProcessor.doProcess(StatusProcessor.java:45)
         at 
org.apache.james.imap.processor.AbstractMailboxProcessor.doProcess(AbstractMailboxProcessor.java:111)
         at 
org.apache.james.imap.processor.AbstractMailboxProcessor.process(AbstractMailboxProcessor.java:98)
         at 
org.apache.james.imap.processor.AbstractMailboxProcessor.doProcess(AbstractMailboxProcessor.java:90)
         at 
org.apache.james.imap.processor.AbstractMailboxProcessor.doProcess(AbstractMailboxProcessor.java:72)
         at 
org.apache.james.imap.processor.base.AbstractChainedProcessor.process(AbstractChainedProcessor.java:57)

Is there any insight on what to do here ?

I am using James 3.4.0 with Spring Configuration and Postgres as database.

Pablo