Bug Transaction failed: Duplicate header 'Auto-Submitted'

[bengineer]

I upgraded our forum 2 days ago to 2.2.15. Since then I have thousands of these errors:

Code:

Swift_TransportException: Email to teresacbaker@aol.com from info@a2oc.net failed: Expected response code 250 but got code "554", with message "554 Transaction failed: Duplicate header 'Auto-Submitted'. "
src/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php:459
Generated by: Unknown account
17 Feb 2024 at 7:21 PM
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