[MlMt] MmSMTPUTF8Enabled

[Benny Kjær Nielsen]

On 4 Mar 2016, at 0:57, Philip Paeps wrote:

> I already found at least one server that doesn't like SMTPUTF8. :)  I 
> was a little surprised that when I sent a test (or more accurately 
> "tëst") email from MailMate with SMTPUTF8 enabled through my server 
> which supports SMTPUTF8 (now) to a third mailserver, I get a bounce 
> complaining about SMTPUTF8 not being supported on the third server.  I 
> would have expected my mailserver to have made appropriate noises to 
> the third mailserver.  Clearly not a MailMate problem though.

It seems that is legal behavior, but it's the easy way out in the 
[RFC](https://tools.ietf.org/html/rfc6531#section-3.2).

When MailMate encounters an SMTP server without SMTPUTF8 then it 
re-encodes all the headers of the email to be sent. Postfix is allowed 
to do the same. Postfix is also allowed to reject the message 
immediately. With a proper response that would have allowed MailMate to 
do the conversion and try again.

Given that Google supports SMTPUTF8 I would have expected it to have 
worked better. Have you tried sending with Google SMTP to see how it 
handles the same problem?

> The same "tëst" message does make it through Postfix and Dovecot to 
> my mailbox as long as I don't try to send it across the internet. :)

Not much of a success, but I guess it's a first step :-)

> I wanted to try out my فيليب@trouble.is alias, but it turns out 
> the To: field in MailMate isn't too happy about bidirectional email 
> addresses.  I can type (or paste) فيليب, but it wants to put the 
> @ on the left of the ف rather than the right of ب.  There seems to 
> be no way to convince the To: field of that (ridiculous -- but real!) 
> email address.
>
> Amazingly, if I paste فيليب@trouble.is, the email bounces, but 
> ... if I paste trouble.is@فيليب it works. :)

Well, if you ignore what is displayed and then take a look at the raw 
message (⌥⌘U) then it does generate this:

	To: فيليب@trouble.is

> So I think MailMate is probably behaving mostly correctly as far as I 
> can tell with an afternoon of testing.  Except for some bidirectional 
> oddities.  But those might just be "Apple".

At least it's not obvious to me that I can do anything about it (but I 
probably know too little about bidirectional text).

> I think I'll need to tame Postfix on my relay to make appropriate 
> noises to servers on the internet that don't speak SMTPUTF8 though.

If it can be told to reject messages immediately when the destination 
server does not support SMTPUTF8 then I could look into making retry 
with a re-encoded message. That might make SMTPUTF8 more useful in 
practice. Current behavior (the bounce) makes it impossible to send the 
message with MailMate.

> I'll keep the option on for the time being to see what breaks.

Thanks! I don't really have time for this myself.

> PS: Happily, there is no "m" in my name, so I can't try out any of the 
> delightful zero-width non-joiners. ;)

I'm just going to ignore that :)

-- 
Benny
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