Re: FW: ban the use and implementation of UTF-7

[Kari Hurtta <hurtta+gmane@siilo.fmi.fi>]

Martin Duerst <duerst@it.aoyama.ac.jp> writes in gmane.ietf.charsets:

> At 23:49 06/12/15, Kari Hurtta wrote:
> 
> >Well, UTF-7 is attractive on mail header fields, because 8-bit is not yet 
> >allowed.
> 
> I don't understand this. Raw 8-bit isn't allowed, but base64 or qp
> can be used (including the identification of the encoding).
> You may be able to put UTF-7 into email header fields, even at
> some positions where you can't put RFC 2047 stuff, but no
> MUA (or MTA, for that matter) will recognize it and use the actual
> characters, which means it's pretty useless.
> 
> Regards,    Martin.


Of course, when UTF-7 used on mail headers, RFC 2047 is used for labeling.

UTF-7 with RFC 2047  simply produces much shorter encoding than
UTF-8 with RFC 2047

UTF-7 is used on here ... :-)


When UTF-7 is used,  RFC 2047's quote-printable encoding do not
encode any characters in practise. It only produces labeling.

Compare

   Subject: =?UTF-7?Q?T+AOQ-ss+AOQ-_esimerkki?=

versus

   Subject: =?UTF-8?Q?T=C3=A4ss=C3=A4_esimerkki?=


On here there was only two non-ascii characters on input.


When there is more non-ascii characters it is more clear:

   Subject: =?UTF-8?Q?=C3=84iti_k=C3=A4vi_t=C3=A4=C3=A4ll=C3=A4?=

versus

   Subject: =?UTF-7?Q?+AMQ-iti_k+AOQ-vi_t+AOQA5A-ll+AOQ-?=


There was 5 non-ascii characters. 



> #-#-#  Martin J. Du"rst, Assoc. Professor, Aoyama Gakuin University
> #-#-#  http://www.sw.it.aoyama.ac.jp       mailto:duerst@it.aoyama.ac.jp     

/ Kari Hurtta