Re: Gnus generates an invalid To header

[Elias Oltmanns <eo@nebensachen.de>]

Tassilo Horn <tassilo@member.fsf.org> wrote:
> Reiner Steib <reinersteib+gmane@imap.cc> writes:
>
> Hi Reiner,
>
>>> Reply-To: "kontakt@tieraerztliche-klinik.com" <Tierklinik Kaiserberg Duisburg>
>>> From: <kontakt@tieraerztliche-klinik.com>
>>>
>>> When I want to reply to it (R or r) Gnus generates the following To
>>> header:
>>>
>>> To: "kontakt@/usr/bin/idn: tld_check_4z: missing inputtieraerztliche-klinik.com" <Tierklinik Kaiserberg Duisburg>
>>
>> This looks like the output of the IDNA program (/usr/bin/idn).  I
>> don't have IDNA installed, so I get (disabling it does the same [1]):
>>
>> ,----
>> | To: "kontakt@tieraerztliche-klinik.com" <Tierklinik Kaiserberg Duisburg>
>> `----
>>
>> This is exactly the bogus Reply-To the sender requested.
>>
>> By edebugging `message-idna-to-ascii-rhs-1', I found that it calls
>> (idna-to-ascii rhs) with `rhs' = "" because the right hand side of
>> "tierklinikkaiserbergduisburg" is the empty string.  Maybe message
>> should just return the same header instead if calling `idna-to-ascii'
>> if `rhs' is empty?
>
> With "the same header" you mean the complete bogus Reply-To header?  I
> don't think that would be good, because then it would possibly be sent
> to a local user.  And sending to a wrong recipient is much worse than
> not sending at all.

What Reiner suggests is fixing a bug on Gnus' part and a priori the
right thing to do.  Your concern is legitimate, but it is a feature
request rather than a bug fix.  After all, the sender is ultimately
responsible for setting a valid Reply-To header and, by failing to do
so, positively asks for trouble.  Also, Reiner's suggestion doesn't even
change anything on the MTA level since the non'comment part of both
example headers (Reiner's and yours) are identical.

That said, it might still be worthwhile to implement the feature you are
asking for.  I recollect two incidents where I tried to reply to emails
only to find out that the Reply-To header was bogus.  However, there
seem to be too many ways to screw the Reply-To header in a way that
results in a syntactically correct but effectively bogus header.  If a
user decides to use fully qualified email addresses only (after all,
there is bbdb and auto completion), gnus can generally warn before
shipping off messages to addresses without a domain part.  This is about
all I can think of right now to tacle this issue and its probably not a
good default setting.

Regards,

Elias