Malformed MIME header line error


I am getting failures when sending email with lots of replies and one or two inline messages. If I cut off parts of the email and maybe an image or two then the email gets sent. Looks like a problem between the email client and the SMTP server.


[SMTP]Cannot send message (Email body not accepted due to the following reason:
"Error: transaction failed, blame it on the weather: malformed MIME header line: iVBORw0KGgoAAAANSUhEUgAAAUAAAADtCAYAAADOZawuAAAAAXNSR0IArs4c6QAAAARnQU1BAACx