<s>
MIMEDefang	B-Protocol
is	O
a	O
GPL	B-License
licensed	B-License
framework	O
for	O
filtering	O
e-mail	O
.	O
</s>
<s>
It	O
uses	O
sendmail	B-Application
's	O
"	O
Milter	B-Application
"	O
API	B-General_Concept
,	O
some	O
C	B-Language
glue	B-General_Concept
code	I-General_Concept
,	O
and	O
some	O
Perl	B-Language
code	O
to	O
let	O
the	O
user	O
write	O
high-performance	O
mail	O
filters	O
in	O
Perl	B-Language
.	O
</s>
<s>
MIMEDefang	B-Protocol
can	O
be	O
used	O
to	O
:	O
</s>
<s>
MIMEDefang	B-Protocol
was	O
originally	O
developed	O
by	O
Dianne	O
Skoll	O
,	O
who	O
was	O
contracted	O
by	O
the	O
Royal	O
College	O
of	O
Physicians	O
and	O
Surgeons	O
of	O
Canada	O
in	O
2000	O
to	O
help	O
stop	O
the	O
flood	O
of	O
email	O
viruses	O
to	O
the	O
college	O
's	O
network	B-Architecture
.	O
</s>
<s>
The	O
software	O
was	O
written	O
to	O
filter	O
attachments	O
and	O
was	O
originally	O
called	O
MIMESweeper	O
,	O
then	O
MIMEDefanger	O
,	O
and	O
currently	O
MIMEDefang	B-Protocol
.	O
</s>
<s>
On	O
December	O
21	O
,	O
2001	O
,	O
a	O
version	O
incorporating	O
support	O
for	O
SpamAssassin	B-Language
was	O
released	O
,	O
making	O
MIMEDefang	B-Protocol
a	O
filter	O
for	O
both	O
spam	O
and	O
viruses	O
.	O
</s>
<s>
Skoll	O
's	O
company	O
,	O
Roaring	O
Penguin	O
Software	O
,	O
developed	O
and	O
sold	O
a	O
commercial	O
anti-spam	O
product	O
known	O
as	O
CanIt	O
,	O
which	O
is	O
based	O
on	O
the	O
open-source	O
version	O
of	O
MIMEDefang	B-Protocol
.	O
</s>
<s>
On	O
March	O
5	O
,	O
2020	O
,	O
AppRiver	O
agreed	O
to	O
give	O
The	O
McGrail	O
Foundation	O
leadership	O
of	O
the	O
open-source	O
MIMEDefang	B-Protocol
project	O
for	O
a	O
period	O
of	O
three	O
years	O
,	O
automatically	O
renewable	O
for	O
one-year	O
terms	O
after	O
that	O
unless	O
either	O
AppRiver	O
or	O
The	O
McGrail	O
Foundation	O
chooses	O
not	O
to	O
renew	O
the	O
agreement	O
.	O
</s>
<s>
The	O
Milter	B-Application
library	O
included	O
with	O
Sendmail	B-Application
uses	O
POSIX	O
threads	B-Operating_System
to	O
allow	O
multiple	O
concurrent	O
filters	O
.	O
</s>
<s>
MIMEDefang	B-Protocol
's	O
Perl	B-Language
filter	O
uses	O
a	O
pre-forked	O
process	O
model	O
,	O
similar	O
to	O
the	O
traditional	O
Apache	B-Application
Web	I-Application
server	I-Application
multi-processing	O
model	O
.	O
</s>
<s>
MIMEDefang	B-Protocol
therefore	O
consists	O
of	O
three	O
components	O
:	O
</s>
<s>
A	O
Perl	B-Language
program	O
called	O
mimedefang.pl	O
that	O
provides	O
the	O
basic	O
filtering	O
infrastructure	O
.	O
</s>
<s>
MIMEDefang	B-Protocol
users	O
code	O
their	O
filtering	O
policies	O
in	O
Perl	B-Language
,	O
using	O
the	O
infrastructure	O
provided	O
by	O
mimedefang.pl	O
.	O
</s>
<s>
They	O
do	O
n't	O
need	O
to	O
worry	O
about	O
thread	B-Operating_System
synchronizations	O
because	O
each	O
Perl	B-Language
filter	O
is	O
a	O
separate	O
single-threaded	B-Operating_System
process	O
.	O
</s>
<s>
The	O
infrastructure	O
provided	O
by	O
mimedefang.pl	O
follows	O
the	O
Milter	B-Application
API	B-General_Concept
reasonably	O
closely	O
,	O
but	O
not	O
exactly	O
.	O
</s>
<s>
It	O
includes	O
convenience	O
routines	O
for	O
parsing	O
and	O
rebuilding	O
MIME	O
messages	O
so	O
that	O
filter	O
authors	O
can	O
concentrate	O
on	O
high-level	O
policy	O
rather	O
than	O
worry	O
about	O
low-level	O
API	B-General_Concept
details	O
.	O
</s>
