<s>
DomainKeys	B-Protocol
(	O
informally	O
DK	O
)	O
is	O
a	O
deprecated	O
e-mail	O
authentication	O
system	O
designed	O
by	O
Yahoo	B-Application
to	O
verify	O
the	O
domain	O
name	O
of	O
an	O
e-mail	O
sender	O
and	O
the	O
message	O
integrity	O
.	O
</s>
<s>
Aspects	O
of	O
DomainKeys	B-Protocol
,	O
along	O
with	O
parts	O
of	O
Identified	O
Internet	O
Mail	O
,	O
were	O
combined	O
to	O
create	O
DomainKeys	B-Protocol
Identified	I-Protocol
Mail	I-Protocol
(	O
DKIM	B-Protocol
)	O
,	O
which	O
is	O
now	O
widely	O
used	O
.	O
</s>
<s>
Both	O
DomainKeys	B-Protocol
and	O
DKIM	B-Protocol
were	O
published	O
in	O
May	O
2007	O
,	O
DomainKeys	B-Protocol
as	O
an	O
"	O
historical	O
"	O
protocol	O
,	O
and	O
DKIM	B-Protocol
as	O
its	O
standards-track	O
replacement	O
.	O
</s>
