|
On Tue, 15 May 2001, Joseph Mack wrote:
> Michael_E_Brown@xxxxxxxx wrote:
> >
> > Wensong,
> >
> > I agree, but... :-)
>
> How would someone like AOL handle the mail farm problem? How
> do users get to their mail? Does everyone in AOL get their
> mail off one machine (or replicated copies of it) or is each
> person directed to one of many smaller machines to get their
> mail? Anything else of relevence to mail farms?
>
> Joe
>
>
Tough question...
AOL has a system of inbound mail relays to receive all their user's mail.
Take a look:
[mebrown@blap opt]$ nslookup
Default Server: ausdhcprr501.us.dell.com
Address: 143.166.227.254
> set type=mx
> aol.com
Server: ausdhcprr501.us.dell.com
Address: 143.166.227.254
aol.com preference = 15, mail exchanger = mailin-03.mx.aol.com
aol.com preference = 15, mail exchanger = mailin-04.mx.aol.com
aol.com preference = 15, mail exchanger = mailin-01.mx.aol.com
aol.com preference = 15, mail exchanger = mailin-02.mx.aol.com
aol.com nameserver = dns-01.ns.aol.com
aol.com nameserver = dns-02.ns.aol.com
mailin-03.mx.aol.com internet address = 152.163.224.88
mailin-03.mx.aol.com internet address = 64.12.136.153
mailin-03.mx.aol.com internet address = 205.188.156.186
mailin-04.mx.aol.com internet address = 152.163.224.122
mailin-04.mx.aol.com internet address = 205.188.158.25
mailin-04.mx.aol.com internet address = 205.188.156.249
mailin-01.mx.aol.com internet address = 152.163.224.26
mailin-01.mx.aol.com internet address = 64.12.136.57
mailin-01.mx.aol.com internet address = 205.188.156.122
mailin-01.mx.aol.com internet address = 205.188.157.25
mailin-02.mx.aol.com internet address = 64.12.136.89
mailin-02.mx.aol.com internet address = 205.188.156.154
mailin-02.mx.aol.com internet address = 64.12.136.121
dns-01.ns.aol.com internet address = 152.163.159.232
dns-02.ns.aol.com internet address = 205.188.157.232
So that is on the recieve side. On the actual user reading their mail
side, things are much different. AOL doesn't use normal SMTP mail. They
have their own proprietary system, which interfaces to the normal internet
SMTP system through gateways. I don't know how AOL does their internal,
proprietary stuff, but I would guess it would be massively distributed
system.
Basically, you can break down your mail-farm problem into two, possibly
three, areas.
1) Mail receipt (from the internet)
2) Users reading their mail
3) Mail sending (to the internet)
Items 1 and 3 can normally be hosted on the same set of machines, but it
is important to realize that these are separate functions, and can be
split up, if need be.
For item #1, the listing above showing what AOL does is probably a good
example of how to set up a super-high-traffic mail gateway system. I
normally prefer to add one more layer of protection on top of this: a
super low-priority MX at an offsite location. (example: aol.com preference
= 100, mail exchanger = disaster-recovery.offsite.aol.com )
For item #2, that is going to be a site policy, and can be handled many
different ways depending on what mail software you use (imap, pop, etc).
The good IMAP software has LDAP integration. This means you can separate
groups of users onto separate IMAP servers. The mail client then can get
the correct server from LDAP and contact it with standard protocols
(IMAP/POP/etc).
For item #3, you will solve this differently depending on what software
you have for #2. If the client software wants to send mail directly to a
smart gateway, you are probably going to DNS round-robin between several
hosts. If the client expects it's server (from #2) to handle sending
email, then things will be handled differently.
--
Michael Brown
|
