Sending E-Mail with MailManager and Attachment will not save it in send folder

When adding a Attachment to a E-Mail and send it with MailManager the E-Mail will not saved in the Send Items (Gesendete Elemente) Folder

Without an Atachment it works ad E-Mail was saved successfully in Send Items (Gesendete Elemente) Folder

Anyway E-mails will send out Correct in both cases to E-Mail receiver