<s>
Halon	B-Application
is	O
a	O
commercial	O
scriptable	O
SMTP	B-Protocol
server	I-Protocol
.	O
</s>
<s>
It	O
's	O
available	O
for	O
Linux	B-Application
as	O
well	O
as	O
a	O
software	O
distribution	O
based	O
on	O
FreeBSD	B-Operating_System
.	O
</s>
<s>
which	O
operates	O
some	O
of	O
the	O
most	O
active	O
(	O
on	O
the	O
basis	O
of	O
the	O
number	O
of	O
domains	O
they	O
support	O
)	O
mail	B-Protocol
servers	I-Protocol
.	O
</s>
<s>
Like	O
Postfix	B-Application
it	O
supports	O
DANE	B-Protocol
,	O
as	O
well	O
as	O
the	O
draft	O
for	O
MTA-STS	O
,	O
for	O
encrypted	O
email	O
transfer	O
.	O
</s>
<s>
It	O
provides	O
other	O
email	O
security	O
features	O
such	O
as	O
spam	O
filtering	O
from	O
CYREN	O
,	O
DMARC	O
and	O
DKIM	B-Protocol
.	O
</s>
