<s>
ZMailer	B-Application
is	O
a	O
SMTP	O
mail	B-Protocol
transfer	I-Protocol
agent	I-Protocol
for	O
Linux	B-Operating_System
,	O
BSD	B-Operating_System
and	O
other	O
Unix-like	B-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
It	O
is	O
intended	O
for	O
gateways	O
or	O
mail	B-Protocol
servers	I-Protocol
or	O
other	O
large	O
site	O
environments	O
that	O
have	O
extreme	O
demands	O
on	O
the	O
abilities	O
of	O
the	O
mailer	O
.	O
</s>
<s>
It	O
was	O
first	O
developed	O
in	O
1988	O
,	O
in	O
reaction	O
to	O
the	O
then	O
existing	O
problems	O
with	O
Sendmail	B-Application
,	O
by	O
Rayan	O
S	O
.	O
Zachariassen	O
at	O
the	O
University	O
of	O
Toronto	O
.	O
</s>
<s>
While	O
official	O
releases	O
have	O
recently	O
been	O
infrequent	O
,	O
regular	O
development	O
and	O
bug-fixes	O
occur	O
in	O
CVS	B-Application
.	O
</s>
<s>
ZMailer	B-Application
supports	O
all	O
the	O
modern	O
features	O
expected	O
in	O
a	O
MTA	B-Protocol
including	O
DNSBL	O
,	O
SPF	B-Protocol
,	O
and	O
message	O
content	O
scanning	O
.	O
</s>
<s>
One	O
site	O
of	O
note	O
utilizing	O
ZMailer	B-Application
is	O
vger.kernel.org,	O
hosting	O
the	O
various	O
Linux	B-Operating_System
kernel	I-Operating_System
mailing	O
lists	O
.	O
</s>
