Possible duplicate headers issue when sending an outbound email with attachment
When sending an internet email with an attachment to certain internet email services, this type of bounce message is returned:
This delivery report was generated by the program amavisd-new at host mail.emailnw.co.uk. Our internal reference code for your message is 16446-01/V3_vqObHzpeD
INVALID HEADER: DUPLICATE HEADER FIELD
Duplicate header field: "Content-Type"
DUPLICATE HEADER FIELD
The RFC 5322 document specifies rules for forming internet messages. Section '3.6. Field Definitions' specifies that certain header fields must not occur more than once in a message header section.
Please let me know if you need any more info.