I'm unable to send and/or produce test emails for large mailings. This seems to be a result of CiviMail not completing the recipient estimation process. Attempting a test email while it's stuck on "estimating" gives this error:
Error in call to Mailing_send_test : Error in call to MailingJob_create : DB Constraint Violation - possibly mailing_id should possibly be marked as mandatory for this API. If so, please raise a bug report
This appears to happen in the neighborhood of 4500 recipients and above.
[I have seen reports that similar issues were resolved in version 4.6.3, but this error occurred in 4.6.9]