Re: [Evolution] How does evo determine when to base64 encode?

["Johnson, Brett E (HP Cloud Linux R&D)" <brett hpe com>]

Thanks Milan, for your help/suggestions!

On Wed, 2016-02-17 at 09:49 +0100, Milan Crha wrote:
> On Tue, 2016-02-16 at 22:25 +0000, Johnson, Brett E (HP Cloud Linux
> R&D) wrote:
> > I've noticed that, using evolution-ews, evolution almost always base64
> > -encodes
> > the body of my messages.  Yet, if I send the same message via SMTP, it is
> > not
> > encoded.
>
>       Hi,
> do you send exactly the same message using Evolution, once through an
> evolution-ews account, another time using SMTP?

Yes.  I sent two message via EWS (one just plain text, and the other with some
minimal html italics/bold).  Then I sent the same messages (using "Edit as new
message") and selecting an evolution IMAP/SMTP account pointing at the same
msexchange server (via the "From:" menu).  The ones sent from the EWS account
are both received as multipart/alternative MIME messages with base64 encoding. 
 When sent from the IMAP/SMTP account, both are received also as
multipart/alternative, but the parts are sent with 7bit ascii encoding. 
 Finally, I composed the exact same message in OWA and sent it, and the result
was the same as evolution/SMTP, except the encoding for the text/html part was
"quoted-printable" instead of "7bit".

> > Can anyone explain this?  Is there any way to turn it off?
>
> I do not think so. If the answer is 'yes' for my question above, then
> it clearly means that it's not done by the message composer, because it
> always produces the same result.

I agree it's not done by the message composer.  It must have something to do
with the EWS transport, but I don't really understand that part.

> > I really don't want to send out base64 encoded blobs to anyone
>
> Why does it matter for you? You see the base64 encoding only if you
> check the message source.

You're making the incorrect assumption that everyone uses a mail client that can
transparently decode mime/base64. I need to be able to send plain text emails,
especially in some circles/mailing lists where sending a non-plaintext email to
the list will get you publicly shamed and even banished.

> By the way, there are circumstances where base64 encoding is required.
> For example if you encrypt the message. The encrypted part contains
> binary data (not text), thus the encoding is required to not have
> modified the data by respective servers on the route from the sender's
> machine to the receiver's machine.

Agreed, I understand this.  I'm not complaining about using base64 when it's
needed, only when it's not needed, and when I'm trying purposefully to send
plain text.

> If you want to debug what the evolution-ews does when it sends the
> message, then run evolution from a terminal like this:
>
>    $ EWS_DEBUG=2 evolution
>
> Then resend any message through the EWS account, once the initial buzz
> will end. You should see in the output something like
>    <messages:CreateItem ...
> (in time of the send) and inside it also
>    <Message><MimeContent>...</MimeContent>
> The content of <MimeContent/> is the message as passed to the server,
> encoded as base64 (that is required here, because the envelope is an
> XML document). I sent a very simple message, which was Subject:test; in
> body:test, and the decoded MimeContent showed:
>    Content-Type: text/plain
>    Content-Transfer-Encoding: 7bit
> thus no base64 in the message itself at all.

Thanks, I tried this, and when sending via EWS, I see the same thing you do. 
 I.e. there's a base64 blob in between the <MimeContent></MimeContent> tags, and
if I decode that blob, it's the same thing that I see in the message sent via
SMTP.  Bizarrely, what appears in the message sent via EWS is the two
multipart/alternative parts, each base64 encoded separately. So, it's apparent
that it's the msexchange server doing the encoding, not evolution.  I wonder why
it's doing that when sent this way, but not when sent via SMTP?

> With respect of the Outlook, I do not know what version of Outlook you
> use, neither what version of the Exchange server you connect to, but
> since Exchange 2007, the servers can be connected through MAPI and EWS. In any
> case, the debugging will show what is passed to the server.

I think the outlook version is 2013, at least that's what the icon says.  And
I'm pretty sure it's connecting via EWS, not MAPI.  In the account
configuration, it has a bizarre-looking "server name" that looks like a UUID of
some sort, and the "Connect to Exchange via HTTP" box is checked.

I don't know what version of exchange is running in the galactic corp HQ.  The
debug output SOAP-ENV I generated above says:

<types:RequestServerVersion xmlns:types="http://schemas.microsoft.com/exchange/services/2006/types"; 
Version="Exchange2010_SP2"/>

Is that a return from a query?  Or is it the version evolution-ews supports?

In any case, I don't really know where to go from here.  Maybe it's a
misconfiguration of the exchange server, or maybe there's something in the
evolution-ews messages that makes exchange think it needs to encode the parts?

-- 
Brett Johnson<brett hpe com>
"Prestige is like a powerful magnet that warps even your beliefs about what you
 enjoy. It causes you to work not on what you like, but what you'd like to like."
  ~~ Paul Graham