<s>
DeltaSync	B-Device
was	O
a	O
proprietary	O
Microsoft	O
communications	O
protocol	O
for	O
synchronizing	O
web	O
services	O
with	O
offline	B-Protocol
clients	I-Protocol
.	O
</s>
<s>
Windows	B-Operating_System
Live	I-Operating_System
Hotmail	I-Operating_System
was	O
connected	O
to	O
offline	B-Protocol
clients	I-Protocol
using	O
DeltaSync	B-Device
;	O
Outlook	O
Connector	O
and	O
the	O
Windows	B-Application
Live	I-Application
Mail	I-Application
client	O
use	O
it	O
for	O
offline	O
access	O
.	O
</s>
<s>
Microsoft	O
pushed	O
for	O
this	O
protocol	O
instead	O
of	O
POP3	B-Protocol
or	O
IMAP4	B-Protocol
for	O
supporting	O
various	O
advanced	O
features	O
,	O
like	O
contacts	O
,	O
calendar	O
,	O
and	O
notes	O
synchronization	O
.	O
</s>
<s>
Using	O
the	O
DeltaSync	B-Device
protocol	O
,	O
Microsoft	O
intended	O
to	O
provide	O
a	O
common	O
platform	O
for	O
any	O
compatible	O
device	O
to	O
implement	O
a	O
client	O
which	O
can	O
two-way	O
synchronize	O
mail	O
,	O
contacts	O
,	O
calendar	O
,	O
and	O
notes	O
.	O
</s>
<s>
In	O
January	O
2007	O
,	O
Microsoft	O
announced	O
DeltaSync	B-Device
as	O
the	O
replacement	O
for	O
WebDAV	B-Protocol
.	O
</s>
<s>
In	O
April	O
2008	O
,	O
Microsoft	O
sent	O
an	O
email	O
warning	O
that	O
WebDAV	B-Protocol
would	O
no	O
longer	O
be	O
supported	O
after	O
30	O
June	O
2008	O
.	O
</s>
<s>
In	O
June	O
2009	O
,	O
Microsoft	O
announced	O
that	O
WebDAV	B-Protocol
support	O
would	O
finally	O
end	O
on	O
1	O
September	O
2009	O
.	O
</s>
<s>
The	O
DeltaSync	B-Device
compression	O
code	O
produces	O
a	O
stream	O
with	O
a	O
four	O
byte	O
magic	O
number	O
of	O
"	O
HU01	O
"	O
,	O
followed	O
by	O
the	O
stream	O
header	O
.	O
</s>
<s>
Since	O
Microsoft	O
migrated	O
the	O
Outlook.com	B-Operating_System
mail	O
to	O
use	O
a	O
structure	O
based	O
on	O
Office	B-Operating_System
365	I-Operating_System
,	O
the	O
DeltaSync	B-Device
protocol	O
was	O
discontinued	O
on	O
30	O
June	O
2016	O
,	O
and	O
mail	O
will	O
not	O
be	O
able	O
to	O
be	O
synced	O
using	O
Windows	B-Application
Live	I-Application
Mail	I-Application
after	O
that	O
time	O
.	O
</s>
<s>
Google	O
's	O
Gmail	O
and	O
some	O
other	O
providers	O
 '	O
mail	O
services	O
still	O
work	O
with	O
DeltaSync	B-Device
.	O
</s>
<s>
Although	O
DeltaSync	B-Device
has	O
sunk	O
,	O
Microsoft	O
's	O
Windows	B-Application
Live	I-Application
Mail	I-Application
2011	O
and	O
2012	O
continue	O
to	O
work	O
with	O
Hotmail	B-Operating_System
e-mail	O
accounts	O
,	O
by	O
using	O
IMAP	B-Protocol
(	O
or	O
,	O
less	O
effectively	O
,	O
POP	O
)	O
in	O
place	O
of	O
DeltaSync	B-Device
.	O
</s>
