<s>
OpenSMTPD	B-Application
(	O
also	O
known	O
as	O
OpenBSD	B-Operating_System
SMTP	B-Protocol
Server	I-Protocol
)	O
is	O
a	O
Unix	B-Operating_System
daemon	I-Operating_System
implementing	O
the	O
Simple	B-Protocol
Mail	I-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
to	O
deliver	O
messages	O
on	O
a	O
local	O
machine	O
or	O
to	O
relay	O
them	O
to	O
other	O
SMTP	B-Protocol
servers	I-Protocol
.	O
</s>
<s>
OpenSMTPD	B-Application
is	O
primarily	O
developed	O
by	O
Gilles	O
Chehade	O
,	O
Eric	O
Faurot	O
and	O
Charles	O
Longeau	O
as	O
part	O
of	O
the	O
OpenBSD	B-Operating_System
project	I-Operating_System
.	O
</s>
<s>
Its	O
design	O
goals	O
include	O
security	O
,	O
reliability	O
,	O
ease	O
of	O
configuration	O
,	O
and	O
support	O
for	O
common	O
use	B-Architecture
cases	I-Architecture
.	O
</s>
<s>
The	O
source	O
code	O
is	O
available	O
under	O
the	O
ISC	B-License
license	I-License
.	O
</s>
<s>
Its	O
portable	O
version	O
,	O
like	O
that	O
of	O
OpenSSH	B-Language
,	O
is	O
developed	O
as	O
a	O
child	O
project	O
which	O
adds	O
the	O
portability	O
code	O
to	O
the	O
OpenBSD	B-Operating_System
version	O
and	O
releases	O
it	O
separately	O
.	O
</s>
<s>
The	O
portable	O
version	O
was	O
initiated	O
by	O
Charles	O
Longeau	O
and	O
adds	O
support	O
for	O
multiple	O
operating	O
systems	O
including	O
NetBSD	B-Device
,	O
FreeBSD	B-Operating_System
,	O
DragonFly	B-Application
BSD	I-Application
,	O
and	O
several	O
Linux	B-Application
distributions	O
.	O
</s>
<s>
The	O
development	O
of	O
OpenSMTPD	B-Application
was	O
motivated	O
by	O
a	O
combination	O
of	O
issues	O
with	O
current	O
SMTP	B-Protocol
daemons	B-Operating_System
:	O
difficult	O
configuration	O
,	O
complicated	O
and	O
difficult	O
to	O
audit	O
code	O
,	O
and	O
unsuitable	O
licensing	O
.	O
</s>
<s>
OpenSMTPD	B-Application
was	O
designed	O
to	O
solve	O
these	O
problems	O
and	O
make	O
mail	O
exchanges	O
accessible	O
to	O
a	O
wider	O
user-base	O
.	O
</s>
<s>
After	O
a	O
period	O
of	O
development	O
,	O
OpenSMTPD	B-Application
first	O
appeared	O
in	O
OpenBSD	B-Operating_System
4.6	O
.	O
</s>
<s>
The	O
first	O
release	O
shipped	O
with	O
OpenBSD	B-Operating_System
5.3	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
OpenSMTPD	B-Application
5.7.2	O
was	O
released	O
to	O
address	O
these	O
issues	O
.	O
</s>
<s>
On	O
28	O
January	O
2020	O
,	O
a	O
vulnerability	O
in	O
OpenSMTPD	B-Application
was	O
disclosed	O
that	O
could	O
be	O
remotely	O
exploited	O
to	O
run	O
arbitrary	O
shell	O
commands	O
as	O
root	O
.	O
</s>
<s>
OpenSMTPD	B-Application
6.6.2	O
was	O
released	O
to	O
fix	O
the	O
vulnerability	O
.	O
</s>
<s>
OpenSMTPD	B-Application
is	O
an	O
attempt	O
by	O
the	O
OpenBSD	B-Operating_System
team	O
to	O
produce	O
an	O
SMTP	B-Protocol
daemon	B-Operating_System
implementation	O
that	O
is	O
secure	O
,	O
reliable	O
,	O
high	O
performance	O
,	O
simple	O
to	O
security	O
audit	O
and	O
trivial	O
to	O
set	O
up	O
and	O
administer	O
.	O
</s>
<s>
As	O
such	O
,	O
the	O
design	O
goals	O
for	O
OpenSMTPD	B-Application
are	O
:	O
security	O
,	O
ease	O
of	O
use	O
,	O
and	O
performance	O
.	O
</s>
<s>
Security	O
in	O
OpenSMTPD	B-Application
is	O
achieved	O
by	O
robust	O
validity	O
check	O
in	O
the	O
network	O
input	O
path	O
,	O
use	O
of	O
bounded	O
buffer	O
operations	O
via	O
strlcpy	O
,	O
and	O
privilege	O
separation	O
to	O
mitigate	O
the	O
effects	O
of	O
possible	O
security	O
bugs	O
exploiting	O
the	O
daemon	B-Operating_System
through	O
privilege	O
escalation	O
.	O
</s>
<s>
In	O
order	O
to	O
simplify	O
the	O
use	O
of	O
SMTP	B-Protocol
,	O
OpenSMTPD	B-Application
implements	O
a	O
smaller	O
set	O
of	O
functionalities	O
than	O
those	O
available	O
in	O
other	O
SMTP	B-Protocol
daemons	B-Operating_System
,	O
the	O
objective	O
is	O
to	O
provide	O
enough	O
features	O
to	O
satisfy	O
typical	O
usage	O
at	O
the	O
risk	O
of	O
unsuitability	O
for	O
esoteric	O
or	O
niche	O
requirements	O
.	O
</s>
