<s>
Haraka	B-Protocol
is	O
an	O
open	O
source	O
SMTP	B-Protocol
server	I-Protocol
.	O
</s>
<s>
The	O
server	O
and	O
its	O
plugins	O
are	O
written	O
in	O
JavaScript	B-Language
using	O
the	O
Node.js	B-Language
framework	O
.	O
</s>
<s>
Haraka	B-Protocol
follows	O
a	O
plugin	O
model	O
,	O
implementing	O
a	O
very	O
lightweight	O
SMTP	B-Protocol
core	O
and	O
providing	O
developers	O
hooks	O
into	O
the	O
mail	O
flow	O
.	O
</s>
<s>
Almost	O
all	O
of	O
Haraka	B-Protocol
's	O
functionality	O
is	O
built	O
as	O
plugins	O
.	O
</s>
<s>
Through	O
its	O
use	O
of	O
the	O
V8	B-Language
JavaScript	I-Language
engine	I-Language
and	O
asynchronous	B-Architecture
I/O	I-Architecture
,	O
the	O
author	O
claims	O
the	O
server	O
is	O
capable	O
of	O
handling	O
thousands	O
of	O
messages	O
per	O
second	O
.	O
</s>
<s>
Bounce.io	O
announced	O
that	O
they	O
regularly	O
handle	O
2	O
to	O
5	O
thousand	O
simultaneous	O
SMTP	B-Protocol
connections	O
with	O
Haraka	B-Protocol
.	O
</s>
<s>
Haraka	B-Protocol
is	O
frequently	O
used	O
as	O
a	O
filtering	O
MTA	O
in	O
front	O
of	O
other	O
MTAs	O
that	O
lack	O
the	O
performance	O
and/or	O
filtering	O
capabilities	O
of	O
Haraka	B-Protocol
.	O
</s>
<s>
Craigslist	O
uses	O
Haraka	B-Protocol
to	O
handle	O
inbound	O
and	O
then	O
forward	O
validated	O
connections	O
to	O
Postfix	O
.	O
</s>
<s>
Bounce.io	O
similarly	O
uses	O
Haraka	B-Protocol
to	O
accept	O
incoming	O
messages	O
and	O
deliver	O
them	O
to	O
their	O
application	O
engine	O
.	O
</s>
<s>
Mail	O
Toaster	O
6	O
uses	O
Haraka	B-Protocol
similarly	O
to	O
accept	O
incoming	O
mail	O
and	O
forward	O
to	O
a	O
qmail	O
based	O
message	O
store	O
.	O
</s>
<s>
SMTP	B-Protocol
Authentication	O
via	O
LDAP	O
,	O
vpopmaild	O
,	O
flat_file	O
,	O
or	O
SMTP	B-Protocol
proxy	O
.	O
</s>
