<s>
Bogofilter	B-Protocol
is	O
a	O
mail	O
filter	O
that	O
classifies	O
e-mail	O
as	O
spam	O
or	O
ham	O
(	O
non-spam	O
)	O
by	O
a	O
statistical	O
analysis	O
of	O
the	O
message	O
's	O
header	O
and	O
content	O
(	O
body	O
)	O
.	O
</s>
<s>
The	O
statistical	O
technique	O
used	O
is	O
known	O
as	O
Bayesian	B-Application
filtering	I-Application
.	O
</s>
<s>
Bogofilter	B-Protocol
's	O
primary	O
algorithm	O
uses	O
the	O
f(w )	O
parameter	O
and	O
the	O
Fisher	O
inverse	O
chi-square	O
technique	O
that	O
he	O
describes	O
.	O
</s>
<s>
Bogofilter	B-Protocol
may	O
be	O
run	O
by	O
a	O
MDA	B-Protocol
or	O
mail	B-Protocol
client	I-Protocol
to	O
classify	O
messages	O
as	O
they	O
are	O
delivered	O
to	O
recipient	O
mailboxes	O
,	O
or	O
be	O
used	O
by	O
a	O
MTA	B-Protocol
to	O
classify	O
messages	O
as	O
they	O
are	O
received	O
from	O
the	O
sending	O
SMTP	O
server	O
.	O
</s>
<s>
Bogofilter	B-Protocol
examines	O
tokens	O
in	O
the	O
message	O
body	O
and	O
header	O
,	O
and	O
refers	O
to	O
wordlists	O
stored	O
by	O
BerkeleyDB	B-Language
,	O
SQLite	B-Language
or	O
QDBM	B-General_Concept
to	O
calculate	O
a	O
probability	O
score	O
that	O
a	O
new	O
message	O
is	O
spam	O
.	O
</s>
<s>
Bogofilter	B-Protocol
provides	O
processing	O
for	O
plain	O
text	O
and	O
HTML	B-Language
and	O
supports	O
reading	O
multi-part	O
MIME	B-Protocol
message	O
including	O
base64	O
,	O
quoted-printable	O
,	O
and	O
uuencoded	O
text	O
or	O
HTML	B-Language
.	O
</s>
<s>
Bogofilter	B-Protocol
ignores	O
non-text	O
attachments	O
,	O
such	O
as	O
images	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
tune	O
Bogofilter	B-Protocol
's	O
statistical	O
algorithms	O
by	O
modifying	O
various	O
coefficients	O
and	O
other	O
settings	O
in	O
its	O
configuration	O
file	O
,	O
or	O
by	O
using	O
the	O
automated	O
bogotune	O
utility	O
included	O
with	O
the	O
software	O
,	O
which	O
attempts	O
to	O
optimise	O
various	O
coefficients	O
to	O
maximise	O
filtering	O
efficiency	O
for	O
a	O
particular	O
corpus	O
of	O
spam	O
and	O
non-spam	O
.	O
</s>
<s>
Standard	O
tests	O
at	O
show	O
that	O
Bogofilter	B-Protocol
compares	O
well	O
to	O
its	O
competitors	O
spambayes	O
,	O
CRM114	O
and	O
DSPAM	O
.	O
</s>
<s>
Bogofilter	B-Protocol
is	O
written	O
in	O
C	B-Language
,	O
and	O
runs	O
on	O
Linux	B-Application
,	O
FreeBSD	B-Operating_System
,	O
NetBSD	B-Device
,	O
OpenBSD	B-Operating_System
,	O
Solaris	B-Application
,	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
,	O
HP-UX	B-Application
,	O
AIX	B-Application
and	O
other	O
platforms	O
.	O
</s>
<s>
It	O
is	O
released	O
under	O
the	O
GNU	B-License
GPL	I-License
.	O
</s>
<s>
The	O
following	O
email	B-Protocol
clients	I-Protocol
are	O
known	O
to	O
support	O
Bogofilter	B-Protocol
as	O
a	O
spam	O
filtering	O
backend	O
:	O
</s>
