Re: Is the "Subject" field of an e-mail an obvious example of "plain text" where no higher level protocol application is possible?

[Jukka K. Korpela]

2012-07-20 19:52, Philippe Verdy wrote:

The "Subject" fi[el]d is subject to special encoding like
Quoted-Printable or Base64 using specific prefixes.

This is a matter of character encoding. All plain text inevitably has 
some encoding, and the encoding may vary without changing the plain text 
status. Admittedly, QP and Base64 may be interpreted as being a 
higher-level protocol, but they can be applied to any plain text, and I 
don’t think this changes plain text to non-plain.

Additionally it has specific formatting conventions related to the use
of spaces and continuation lines if needed.

This is a real deviation from plain text principles and applies to 
e-mail message headers in general. As per clause 2.2.3 of RFC 2822, the 
header is logically a single line but may contain CR LF, which will be 
unfolded.

Yucca