I'm way out of touch on this. Is it now so unusual for someone to have problems
opening a .doc file that ISPs rather than Microsoft & the sender
"up"-grading their application are/is the first to be blamed?
Dav(e/id/o/y) I believe it is long overdue for lawyers, economists, writers &
politicians to understand that ignorance of the law(s of physics) is no excuse!
(BTW I check same title(a)Gmail.com more often)
On Wed, 18/12/13, Russell Coker <russell(a)coker.com.au> wrote:
Subject: Re: [luv-talk] ISP alters attachments
Received: Wednesday, 18 December, 2013, 12:42 AM
On Tue, 17 Dec 2013 21:08:58 Daniel
I suppose you could always send yourself a .doc file
a few via the
said ISP, and compare the one you receive back to the
original and see
if there is any difference.
I can see a situation where ISPs would scan attachments
for malware etc,
but not alter the file.
There are ways of altering the binary message which
shouldn't change the
result when it's decoded. One example is base64 vs
mime encoding, one could
theoretically write a mail server that converted one to the
other with most
users not noticing a difference.
Messages with DKIM signatures can be checked. So if
someone sends you a
message from Gmail or any other service that reliably runs
DKIM then you can
verify the contents. Does anyone know of a good script
to check a DKIM
message? I've got some hacky ones that I wrote, I
could tidy one up and
release it if there's nothing better.
Historically some relatively popular MTAs altered
messages. For example the
Netscape iPlanet MTA would remove leading spaces in header
fields, so subjects
of " test" and "test" would end up the same when the message
The Qmail POP server would add an extra blank line at the
end of each message.
When I was writing my Postal mail benchmark program and
using it to check
message integrity I had special-case code for iPlanet and
Qmail to deal with
this. While such alterations wouldn't affect an
attachment, the people who
break such things might break other things, I could easily
imagine the authors
of either of those programs happily breaking attachments
that they considered
to be wrong.
In regard to the original question if "many ISPs" means
"dozens out of tens of
thousands in the world" then it's likely to be a correct
statement. But if
"many ISPs" means and significant fraction of the ISPs or
the ISP customer
base then I don't think so. Attachments usually work
for most people, the
vast majority of ISPs get it right - or get it wrong in rare
Strangely some people think that infected email should be
(modified) and sent on. I think that ideally it should
be rejected with a
SMTP 55x code and if that fails it should be
discarded. If you know the
message is bad then the recipient should never see it.
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
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