Hi all, Hi all, If we have two MX records with the same preference(like yahoo.com..), will the mails randomly be accepted by each of them? If we set the two SMTP hosts on the connector, will mails randomly sent out through each of them? Thank you.

Hi Round robin will be used AFAIK, so yes.. something around 50% eachJonas Andersson MCTS: Microsoft Exchange Server 2007/2010 | MCITP: EMA 2007/2010 | MCSE/MCSA Blog: http://www.testlabs.se/blog

It really depends on the sending server. I don't think you can guarantee it either way. Some servers will do a lookup, cache the result and always use the same server until the cache expires. Others will do a lookup each time and use whichever one comes first. The only way that you would get close is to having some control is to have a single MX record but with multiple hosts. For example AOL: C:\>nslookup Default Server: server.int.local Address: 192.168.3.2 > set type=mx > aol.com Server: server.int.local Address: 192.168.3.2 Non-authoritative answer: aol.com MX preference = 15, mail exchanger = mailin-02.mx.aol.com aol.com MX preference = 15, mail exchanger = mailin-03.mx.aol.com aol.com MX preference = 15, mail exchanger = mailin-04.mx.aol.com aol.com MX preference = 15, mail exchanger = mailin-01.mx.aol.com C:\>nslookup mailin-02.mx.aol.com Server: server.int.local Address: 192.168.3.2 Non-authoritative answer: Name: mailin-02.mx.aol.com Addresses: 205.188.190.1 64.12.90.65 205.188.103.1 205.188.155.110 Whatever you do, don't put hosts with different MX values, as the higher value will receive more spam. You will notice that both AOL and Yahoo (to use the two examples) have their MX records with the same cost for all hosts to balance the spam load. Simon.Simon Butler, Exchange MVP http://blog.sembee.co.uk http://exbpa.com/

Simon, Thank you for your detailed help. >Whatever you do, don't put hosts with different MX values, as the higher value will receive >more spam. You will notice that both AOL and Yahoo (to use the two examples) have their MX >records with the same cost for all hosts to balance the spam load. Non-authoritative answer: >aol.com MX preference = 15, mail exchanger = mailin-02.mx.aol.com >aol.com MX preference = 15, mail exchanger = mailin-03.mx.aol.com >aol.com MX preference = 15, mail exchanger = mailin-04.mx.aol.com >aol.com MX preference = 15, mail exchanger = mailin-01.mx.aol.com all made sense. What about troubleshooting if users complain about not receiving certain emails from outside? Which MX exchanger should we track on since they have the same preference? Would it be more difficult since they have same prefrence and we do not know which mail exchanger the mails were sent to? Thank you. Thank you.

Your only option is to have logging enabled on everything, then you will have to go through the logs. However it is very difficult to prove a negative, particularly as there are so many things that can stop an email from being delivered that are outside of your control. I often compare email delivery to sending a letter in the post. You know it is coming if someone tells you, but until it is in your hands, you have no control over where it has gone, who is dealing with the delivery. You basically cross your fingers and hope it arrives. Simon.Simon Butler, Exchange MVP. http://blog.sembee.co.uk , http://exbpa.com/

“In addition, two IP addresses (mail hosts) are associated with each MX record. Why two IP addresses per MX record? Because some message transfer agents (MTAs) will always pick the same MX record, no matter how many MX records you have configured for a domain” ---------Refer to <Load Balancing, Edge Transport, and More>James Luo TechNet Subscriber Support (http://technet.microsoft.com/en-us/subscriptions/ms788697.aspx) If you have any feedback on our support, please contact tngfb@microsoft.com