On 29 Mar 2021, at 10:25, Loren Wilton wrote:
I would not be so broad with that. I have 49 messages in my personal
archives with X-MC-User headers, none of which I have classified as
spam.
Bill, do you see multiple X-MC- headers in the mails that come thru
MailChimp?
As in, "multiple many" or "multiple 2 or 3"? Or just the Users header?
After a closer look, it appears that each of those 49 contains ONLY the
X-MC-User header.
That closer look also indicates that other mail providers use various
X-MC-* headers. Notably Mimecast and MailChannels. I have substantial
quantities of entirely person-to-person messages with
X-MC-Loop-Signature, X-MC-Ingress-Time, and X-MC-Unique headers as well
as a few with X-MC-Relay, X-MC-Mailinglist, X-MC-Metadata, and
X-MC-Track. For example, I have tech support conversations with
customers-of-customers who have those in their mail.
So: I rescind my agreement with the "100% targeted advertising"
judgment.
I can't tell from the MailChimp documentation whether the headers will
be generally filtered from the final email message, or passed through.
The majority of them are instructions to MailChimp to do something in
either the headers or body of the message, so really it makes little
sense to leave them in the final message.
I can write rules to detect bogus values for quite a few of the
headers, but the allowed text for a lot of the headers is moderately
complicated, so gets to be a big and expensive regex. It would be a
lot easier to just add points if there are say 3 or more X-MC headers
in a row. But of course that is no good if MC does just pass all the
direction headers through to the final messages it generates.
Based on my ANECDOTAL (as it is just mail in my archives, including a
mix of work and personal accounts) evidence, I would guess that
MailChimp only preserves X-MC-User, but that the other M*C* email
service providers have other possibly colliding X-MC-* headers which
occur in some highly wanted but weakly predictable email in uncertain
combinations.
TL;DR: Be careful, it is complicated.
--
Bill Cole
b...@scconsult.com or billc...@apache.org
(AKA @grumpybozo and many *@billmail.scconsult.com addresses)
Not Currently Available For Hire
