27. The string ”user = @ user.com turbo-smtp.com; On behalf of; <firstname.lastname@example.org>”, appears in recipient's sender field . What does it mean?
This string is not the result of an error. It contains information on the service used to send a particular email.
When you use an SMTP service, the default settings of a mail client ensure that this information is visible to the recipient of the email. The only action available is to remove from the string the name of the service used (in this case "turboSMTP").
Users who have activated the "White Labeled" service can take advantage of this service.