<s>
Smtp-sink	O
is	O
a	O
utility	O
program	O
in	O
the	O
Postfix	B-Application
Mail	I-Application
software	O
package	O
that	O
implements	O
a	O
"	O
black	O
hole	O
"	O
function	O
.	O
</s>
<s>
It	O
accepts	O
Simple	B-Protocol
Mail	I-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
SMTP	B-Protocol
)	O
messages	O
from	O
the	O
network	O
and	O
discards	O
them	O
.	O
</s>
<s>
It	O
is	O
not	O
SMTP	B-Protocol
protocol	I-Protocol
compliant	O
.	O
</s>
<s>
Connections	O
can	O
be	O
accepted	O
on	O
IPv4	B-Protocol
or	O
IPv6	B-Protocol
endpoints	O
,	O
or	O
on	O
UNIX-domain	O
sockets	O
.	O
</s>
<s>
IPv4	B-Protocol
and	O
IPv6	B-Protocol
are	O
the	O
default	O
.	O
</s>
<s>
This	O
program	O
is	O
the	O
complement	O
of	O
the	O
smtp-source(1 )	O
program	O
.	O
</s>
