Using Drupal 7 and Civi 5.7.0
When sending batch emails using CiviMail, if I select "Administer CiviCRM » Scheduled Jobs" and select "Process now" on the "Send Scheduled Mailings" job then the mailing sends successfully. If I allow the cron to execute the same job, then I'm getting an SMTP error ("Failed to set sender" and "authentication failure") and the mailing fails. The log entries for the two jobs are identical. The SMTP settings are correct. The user specified in the cron job is the same as the one I'm using to "Process now".
Note: I recently dealt with the time zone error described in process_mailing processing addresses when called in UI but not CRON This got my cron running the process_mailing job but now I'm getting the SMTP error. The only change I made was to set the timezone on the server to the same as Drupal.