<s>
X-No-Archive	B-Protocol
,	O
also	O
known	O
colloquially	O
as	O
xna	O
,	O
is	O
a	O
newsgroup	B-Application
message	B-General_Concept
header	I-General_Concept
field	O
used	O
to	O
prevent	O
a	O
Usenet	B-Application
message	O
from	O
being	O
archived	O
in	O
various	O
servers	B-Application
.	O
</s>
<s>
The	O
need	O
for	O
X-No-Archive	B-Protocol
began	O
when	O
DejaNews	B-Application
debuted	O
in	O
1995	O
.	O
</s>
<s>
DejaNews	B-Application
was	O
the	O
first	O
large-scale	O
commercial	O
attempt	O
to	O
archive	O
the	O
Usenet	B-Application
news	I-Application
feed	O
,	O
and	O
several	O
newsgroup	B-Application
participants	O
were	O
concerned	O
about	O
privacy	O
rights	O
and	O
about	O
the	O
possibility	O
that	O
their	O
messages	O
could	O
be	O
re-posted	O
through	O
DejaNews	B-Application
in	O
the	O
future	O
.	O
</s>
<s>
DejaNews	B-Application
addressed	O
these	O
concerns	O
by	O
announcing	O
that	O
it	O
would	O
not	O
archive	O
Usenet	B-Application
messages	O
containing	O
the	O
X-No-Archive	B-Protocol
header	B-General_Concept
field	O
.	O
</s>
<s>
X-No-Archive	B-Protocol
was	O
designed	O
to	O
follow	O
the	O
standard	O
message	B-General_Concept
header	I-General_Concept
protocol	O
,	O
RFC	O
1036	O
and	O
RFC	O
977	O
,	O
used	O
in	O
existing	O
newsgroups	B-Application
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
standard	O
header	B-General_Concept
fields	I-General_Concept
used	O
in	O
all	O
newsgroup	B-Application
messages	O
(	O
including	O
Path	O
:	O
,	O
From	O
:	O
,	O
Subject	O
:	O
,	O
and	O
Date	O
:	O
)	O
,	O
news	O
reader	O
software	O
allows	O
a	O
user	O
to	O
add	O
optional	O
fields	O
to	O
a	O
header	B-General_Concept
.	O
</s>
<s>
According	O
to	O
RFC	O
822	O
,	O
these	O
additional	O
fields	O
are	O
prefixed	O
with	O
the	O
label	O
X	O
-	O
so	O
that	O
they	O
can	O
be	O
ignored	O
by	O
news	B-Application
servers	I-Application
and	O
newsreaders	O
.	O
</s>
<s>
The	O
phrase	O
"	O
No	O
Archive	O
"	O
was	O
coined	O
as	O
a	O
way	O
to	O
state	O
"	O
Do	O
not	O
archive	O
this	O
message	O
,	O
"	O
and	O
the	O
X	O
-	O
prefix	O
was	O
added	O
to	O
complete	O
the	O
term	O
X-No-Archive	B-Protocol
.	O
</s>
<s>
The	O
proper	O
field	O
to	O
prevent	O
a	O
message	O
from	O
being	O
archived	O
is	O
:	O
X-No-Archive	B-Protocol
:	O
Yes	O
(	O
abbreviated	O
as	O
"	O
XNAY	B-Protocol
"	O
)	O
.	O
</s>
<s>
This	O
is	O
useful	O
for	O
those	O
users	O
who	O
cannot	O
change	O
the	O
header	B-General_Concept
of	O
messages	O
they	O
send	O
out	O
.	O
</s>
<s>
If	O
the	O
X-No-Archive	B-Protocol
field	O
is	O
set	O
to	O
"	O
No	O
"	O
,	O
or	O
the	O
field	O
is	O
absent	O
,	O
a	O
Usenet	B-Application
archive	O
will	O
not	O
recognize	O
a	O
prohibition	O
on	O
archiving	O
the	O
message	O
.	O
</s>
<s>
When	O
DejaNews	B-Application
was	O
purchased	O
by	O
Google	B-Application
,	O
Google	B-Application
continued	O
to	O
honor	O
the	O
X-No-Archive	B-Protocol
directive	O
.	O
</s>
<s>
Other	O
newsgroup	B-Application
archiving	O
services	O
have	O
also	O
followed	O
in	O
DejaNews	B-Application
 '	O
footsteps	O
,	O
though	O
the	O
decision	O
not	O
to	O
archive	O
X-No-Archive	B-Protocol
messages	O
has	O
been	O
entirely	O
voluntary	O
.	O
</s>
<s>
Many	O
popular	O
newsreader	O
and	O
posting	O
software	O
programs	O
,	O
such	O
as	O
Forté	B-Protocol
Agent	I-Protocol
,	O
include	O
,	O
as	O
a	O
standard	O
option	O
,	O
the	O
ability	O
to	O
insert	O
an	O
X-No-Archive	B-Protocol
field	O
into	O
messages	O
at	O
the	O
user	O
's	O
request	O
.	O
</s>
<s>
Mozilla	B-Application
Thunderbird	I-Application
has	O
the	O
ability	O
to	O
insert	O
custom	O
fields	O
into	O
the	O
header	B-General_Concept
of	O
both	O
email	O
and	O
Usenet	B-Application
messages	O
.	O
</s>
<s>
However	O
,	O
custom	O
fields	O
are	O
not	O
automatically	O
inserted	O
into	O
messages	O
by	O
Thunderbird	B-Application
-	O
the	O
user	O
must	O
add	O
them	O
manually	O
to	O
each	O
message	O
as	O
desired	O
.	O
</s>
