Messages that flow through the global pipeline get their headers cooked, which basically means that their headers go through several mostly unrelated transformations. Some headers get added, others get changed. Some of these changes depend on mailing list settings and others depend on how the message is getting sent through the system. We’ll take things one-by-one.
>>> mlist = create_list('[email protected]') >>> mlist.subject_prefix = ''
When the message’s metadata has a noack key set, an
X-Ack: no header is
X-Ack header in the original message is removed.