I'm new to Zimbra and new to my job which involves some Zimbra administration. I'm hoping the Zimbra community can help me make a good first impression with my new employer.

My question: Can/does Zimbra strip out X-headers on bounced e-mails? If so, can I configure it not to?

I'm evaluating a product called Interspire Email Marketer. It adds several custom X-headers that it uses for bounce processing (X-Mailer-SID is one of them).

When I send an email to a valid address, I see these headers. When I send to an invalid address, these headers are gone in the returned "Delivery Status Notification (Failure)" email.

Interspire cannot process the bounce unless these headers are present.

I can't say for certain Zimbra is responsible for removing the headers. I'd just like to know if it's a possibility and where to look if it is.

Thank you much.