Bill said:
Dear All
If POP server and SMTP server are different server,
so the DNS MX record shoud point to POP server or SMTP server?
SMTP.
SMTP are your inbound servers FROM OTHER EMAIL servers.
(They are also the outbound email servers for your clients and
TO other email systems.)
Pop servers are inbound email servers for YOUR CLIENTS.
Frequently they are on the same machine so many people have
successfully exchanged the two in client configuration or MX
records and gotten lucky.
Frequently the Pop server is on the SMTP server with the lowest
numeric MX record (high priority) and another SMTP server is
the backup SMTP server.
Reason: The POP server usually needs to be on a single server
since some clients can only configure on POP server and the
client machines much in any case find the POP server where their
mail is physically loaded.
In this case, the second SMTP server is usually setup to merely
accept the email (from others) and hold it, until the first SMTP
server with the POP server requests that email from the second
SMTP server.
Since they run in conjunction it is easy for new mail admins to
get them confused.
Mnemonic: POP servers are like the post office BOXES at you
local P.O. (or even like you mailbox in front of you house) where
you must always visit the same location in order to send mail
from a client machine.
SMTP servers are like the P.O. DESK where you can go to any
P.O. -- even while traveling --- and send you mail. In fact, when
traveling you should prefer the CLOSEST P.O. <grin> and use
that one (in the same city, part of town.)
The analogy breaks down when you recognize that your home
mailbox serves both purposes which is perhaps a good reason
for sticking to the analogy of the P.O. Boxes IN a P.O.
