Remove CIVICRM_FLEXMAILER_HACK_DELIVER
I started looking at fixing the memory leaks in MailingJob::runJobs (see #2073) - which is tested via MailingJob:;testMailerSendTest_email but the fact we pass $job out - to use memory & queries efficiently $job should be a CRM_Core_DAO::executeQuery() object but it is a CRM_Mailing_BAO_MailingJob - there are also a couple of places that call functions on it that could be called statically if it were a $dao
Basically we should clear the mess up - or as a minimum for this ticket remove those weird constants CIVICRM_FLEXMAILER_HACK_DELIVER
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