<s>
GNU	B-Application
Anubis	I-Application
is	O
open-source	B-Application
software	I-Application
for	O
processing	O
outgoing	O
email	O
.	O
</s>
<s>
It	O
operates	O
between	O
the	O
mail	B-Protocol
user	I-Protocol
agent	I-Protocol
(	O
MUA	O
)	O
and	O
mail	B-Protocol
transport	I-Protocol
agent	I-Protocol
(	O
MTA	O
)	O
,	O
and	O
can	O
perform	O
various	O
processing	O
and	O
conversion	O
in	O
accord	O
with	O
the	O
sender	O
's	O
specified	O
rules	O
,	O
based	O
on	O
a	O
configurable	O
regular	B-Language
expressions	I-Language
system	O
.	O
</s>
<s>
It	O
operates	O
as	O
a	O
proxy	B-Application
server	I-Application
,	O
independently	O
from	O
mail	B-Protocol
user	I-Protocol
agents	I-Protocol
.	O
</s>
