need your help. 06-29-10

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Hi all,

If you have two same weight(preference) MX records, will inbound emails 
load-balance each other?  if one fails, will it relay mails to the second one?
If you have two smart hosts on the connector, will it automatically 
load-balance each other? 

thank you.
0
Reply Utf 6/29/2010 5:43:20 PM

On Tue, 29 Jun 2010 10:43:20 -0700, ed <ed@discussions.microsoft.com>
wrote:

>If you have two same weight(preference) MX records, will inbound emails 
>load-balance each other?  

That depends on the DNS and the resolver. If DNS uses "round-robin"
the answer would be "probably", but it's still up to the transmitting
client to pick an address from the set of results returned by the
query.

>if one fails, will it relay mails to the second one?

Usually, yes. But it won't "relay", it'll just send the mail to the
next hop.

>If you have two smart hosts on the connector, will it automatically 
>load-balance each other? 

I wouldn't depend on that. Load balancing is a lot more than just
flip-flopping between a pair of IP addresses.
---
Rich Matheisen
MCSE+I, Exchange MVP
0
Reply Rich 6/29/2010 11:29:08 PM

Rich,

thank you.  sorry and I change my questions as follows:

>If you have two same weight(preference) MX records, will inbound emails >randomly be accepted by  each MX record? (check the yahoo's mx records and all >have the same weight)
 

> If you have two smart hosts on the connector, will mails randomly be sent out to each smart host?
  


0
Reply Utf 7/2/2010 7:00:30 PM

On Fri, 2 Jul 2010 12:00:30 -0700, ed <ed@discussions.microsoft.com>
wrote:

>thank you.  sorry and I change my questions as follows:
>
>>If you have two same weight(preference) MX records, will inbound emails >randomly be accepted by  each MX record? (check the yahoo's mx records and all >have the same weight)

The answer is still "it depends".

If your DNS uses round-robin then the answer to each query will put a
different MX record in the 1st position. If the client uses the 1st MX
in the answer then you have a rough form of connection distribution
(but not really "load balancing").

You can accomplish the same thing with just one MX, though. For
example:

domain.com.      IN MX 10  mail.comain.com.
mail.domain.com. IN A      1.2.3.4
mail.domain.com. IN A      1.2.3.5

>> If you have two smart hosts on the connector, will mails randomly be sent out to each smart host?

Not randomly, but certainly to both.
---
Rich Matheisen
MCSE+I, Exchange MVP
0
Reply Rich 7/2/2010 9:29:12 PM

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