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From: ed on 29 Jun 2010 13:43 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.
From: Rich Matheisen [MVP] on 29 Jun 2010 19:29 On Tue, 29 Jun 2010 10:43:20 -0700, ed <ed(a)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
From: ed on 2 Jul 2010 15:00 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?
From: Rich Matheisen [MVP] on 2 Jul 2010 17:29
On Fri, 2 Jul 2010 12:00:30 -0700, ed <ed(a)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 |