Scenario: I use SmtpClient to send message (previously received from Exchange Online) to the smart host. According to RFC I need to add Received header, so that it appears before all other headers.
Thank you for contacting Aspose Support team.
There is no “Insert” method at present to achieve this. We have logged this requirement as EMAILNET-35222 in our issue tracking system for further consideration by our Product team and will update you here once there is some information available in this regard.