Appendix introduction of mail system – AirLive ES-4000 v2 User Manual
Page 166
162
A
A
A
p
p
p
p
p
p
e
e
e
n
n
n
d
d
d
i
i
i
x
x
x
I
I
I
n
n
n
t
t
t
r
r
r
o
o
o
d
d
d
u
u
u
c
c
c
t
t
t
i
i
i
o
o
o
n
n
n
o
o
o
f
f
f
M
M
M
a
a
a
i
i
i
l
l
l
S
S
S
y
y
y
s
s
s
t
t
t
e
e
e
m
m
m
A mail server acts as an intermediate between the Internet and users when sending or receiving mails. The
format of email address looks like [email protected]. Info on the left side of at sign (@) indicates an
account name, the other side stands for the host name.
For instance, you are sending a mail to [email protected], your email software will go to your DNS server
for the IP address and mail exchanger record that corresponding to mail server. Mails will go to mail
exchanger before sending to the host server, in this case, it is yahoo.com.tw. If the DNS server has more than
one MX, then mails will be sent to the MX with the highest priority. Provided that there is no MX, mails will not
be delivered until the corresponding IP has found. When mails have been delivered to yahoo.com.tw, mails
will be distributed to the user according to its account name which shows on the left side of at sign (@).
Process of an email transmission:
The transmissions are divided into three parts, namely MUA, MTA and MDA.
MUA (Mail User Agent):
Whether sending or receiving mail, the end-user client must account on the
MUA which provided by the OS, for end-user client can not send mail directly. Outlook Express is a kind
of the MUA. It serves as a mail deliver and recipient, and enables user to view and edit mails.
MTA (Mail Transfer Agent):
Outgoing and incoming mails are all done by MTA. It allows user to:
1.
Receive mails from other host. As long as user has a account under MTA, then the user will be able
to receive mail.
2.
Sent out mails. On condition that the user has the authority, he will be able to send out mails.
3.
Receive personal mails. User can retrieve and view mails that saved on the mail server.
Usually, MTA refers to a mail server.
MDA (Mail Delivery Agent):
distributes incoming mails of MTA to local mail accounts according to their
account names or sends them to the next MTA.