<s>
A	O
mail	B-Protocol
retrieval	I-Protocol
agent	I-Protocol
(	O
MRA	O
)	O
is	O
a	O
computer	B-Application
application	I-Application
that	O
retrieves	O
or	O
fetches	O
e-mail	O
from	O
a	O
remote	O
mail	B-Protocol
server	I-Protocol
and	O
works	O
with	O
a	O
mail	B-Protocol
delivery	I-Protocol
agent	I-Protocol
to	O
deliver	O
mail	O
to	O
a	O
local	O
or	O
remote	O
email	O
mailbox	O
.	O
</s>
<s>
MRAs	O
may	O
be	O
external	O
applications	O
by	O
themselves	O
or	O
be	O
built	O
into	O
bigger	O
applications	O
like	O
a	O
mail	B-Protocol
user	I-Protocol
agent	I-Protocol
.	O
</s>
<s>
Significant	O
examples	O
of	O
standalone	O
MRAs	O
include	O
fetchmail	B-Protocol
and	O
getmail	B-Protocol
.	O
</s>
<s>
Although	O
they	O
operate	O
like	O
mail	B-Protocol
transfer	I-Protocol
agents	I-Protocol
,	O
MRAs	O
are	O
technically	O
clients	O
when	O
they	O
retrieve	O
and	O
submit	O
messages	O
.	O
</s>
<s>
The	O
mail	B-Protocol
retrieval	I-Protocol
agent	I-Protocol
may	O
support	O
delivery	O
of	O
retrieved	O
mail	O
via	O
the	O
following	O
mechanisms	O
:	O
</s>
<s>
This	O
enables	O
a	O
mailserver	B-Protocol
to	O
have	O
a	O
centrally	O
configured	O
mail	O
retriever	O
agent	O
that	O
runs	O
against	O
a	O
dedicated	O
mail	O
system	O
account	O
,	O
and	O
collects	O
the	O
mail	O
for	O
all	O
users	O
in	O
a	O
single	O
invocation	O
(	O
rather	O
than	O
using	O
cron	B-General_Concept
to	O
run	O
a	O
mail	O
retriever	O
agent	O
against	O
all	O
the	O
mail	O
recipients	O
)	O
.	O
</s>
