On 2022-06-16 at 04:10:41 UTC-0400 (Thu, 16 Jun 2022 01:10:41 -0700)
Jeremy Hansen <jer...@skidrow.la>
is rumored to have said:
Is there an established recipe or utility or filter I can configure to
quarantine html emails?
This would need to be a milter or content_filter. One could implement
this in MIMEDefang or MailMunge (both milters) or possibly using a Sieve
implementation in the delivery chain (e.g. Dovecot has a Sieve module.)
To the best of my knowledge, there's no widely used recipe or tool that
you can just drop in place to get a usable quarantine system.
Bonus would be to process these emails to convert to a full image
removing links and remote images from the quarantined email.
That's not just hard, it's bad. :)
I realize links would have to be pulled to generate the image but
ultimately I would like the end user to just get an image
representation of what the html email would look like with no links or
link following by the MUA.
Therein lies the badness.
Remote retrieval of links within email should only ever happen by the
explicit intentional action of a human user. Images in HTML email that
have remote sources (as opposed to 'cid:' links to included MIME parts)
are used as surveillance tools by senders. Fetching and displaying those
will always tell the sender that the message has been viewed, or at
least that's what email marketers like to tell customers. In practice,
many MUAs only fetch remote resources in mail when explicitly told to do
so, so "open rates" are just so much snake oil, so it isn't as if you
would be destroying a useful metric, you'd just be spoiling it in the
oppoosite direction as most existing breakage. If email marketers come
to believe that sending to addresses on your system makes their "open
rates" look really good, guess what happens...
Rendering the HTML without remote resources is certainly possible, but
often the appearance is quite wrong without them.
--
Bill Cole
b...@scconsult.com or billc...@apache.org
(AKA @grumpybozo and many *@billmail.scconsult.com addresses)
Not Currently Available For Hire
