Several Transport Hub servers

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This topic contains 6 replies, has 4 voices, and was last updated by Avatar shefi 4 years, 5 months ago.

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  • loureed4
    loureed4
    Participant
    #164981

    Hello,

    I am learning Exchange and I read: “You can set up a Transport Hub server in each site” and “You can set up several Transport Hub servers within a site.”

    My question regarding the first quoted stament is: If I set my public mx record pointing to the ip of one of my sites and if that router goes down, how can then the emails reach the other site?.

    Maybe I could set two or three public mx record with different priorities?.

    And for the second statement (“You can set up several Transport Hub servers within a site.”) I have a question too:

    Should I set two or three private mx records with different priorities?

    Thanks in advance!

    Avatar
    Sembee
    Member
    #261436

    Re: Several Transport Hub servers

    You can have as many servers in your MX records as you like.
    You can deliver email to any Exchange server in the forest, Exchange will ensure it is delivered to the correct place.

    Just ensure that you have the same level of spam protection on all servers that are available from the internet.

    The Hub Transport role has gone away in Exchange 2013.

    Simon.

    Avatar
    pjhutch
    Member
    #312778

    Re: Several Transport Hub servers

    Yes, you can have more than one MX record, with different priorities or even have 2 or more with same priority to load balance them.

    Avatar
    shefi
    Member
    #379843

    Re: Several Transport Hub servers

    Many thanks both!

    So, pardon me if the question is too basic but then, a company can have in the public domain:

    mx= 212.23.34.45 priority=1
    mx= 92.182.212.12 priority=5
    mx= 80.8.6.43 priority=10

    But I don’t understand something:

    All the incoming requests go to the first above mx record?, This is, all the requests to the same site?.

    I am planning to set up a DAG in Exchange 2010, therefore all the mailboxes will be replicated , but I don’t know how to tell the requesters to go to any of those above IPs, not only for the first one (212.23.34.45).

    I am a bit confused.

    THANKS ONCE MORE!

    Avatar
    Sembee
    Member
    #261443

    Re: Several Transport Hub servers

    MX records cannot be IP addresses. That is invalid.
    MX records are A records only.

    Therefore if you have three locations you can either

    a. Configure three separate A records (mail1.example.com, mail2.example.com and mail3.example.com) and have all of them in the MX record list.

    b. Configure a single A record with all three IP addresses listed.
    Not a recommended solution though because it makes setting up a PTR for outbound email almost impossible.

    c. Use one of the cloud load balancing services to balance the load. This means all of your MX records point to their service, then you point their service to your own servers.

    The theory in MX records is that priority controls which server gets most of the email. However these days I ignore priority. I have a long term (over seven years now) experiment running with a client, where I track the inbound email to two MX records, one with a cost of 10, one with a cost of 20.
    The record with the cost of 20 received about 20% of the email, but over 90% of all spam.
    As such, I now set all MX records to 10. If you want email to be delivered to all of the hosts, just set them all to 10.

    Simon.

    Avatar
    shefi
    Member
    #379844

    Re: Several Transport Hub servers

    Thanks Sembee,

    So,

    mail1.domain.com = 80.40.20.10
    mail2.domain.com = 90.70.50.30
    mail3.domain.com = 100.80.50.45

    But then I have to configure the clients with one of those three mx records? . If one of them loses connectivity, I could redirect them to one of the other two mx records, manually and only manually?.

    I did not understand when you say to set only one a record with the three IPs, I think that would go:

    mail.domain.com IP1
    mail.domain.com IP2
    mail.domain.com IP3

    But then, the client always goes to IP1 ?.

    I am an utter ignorant because I did not know you could set an A record with three different IPs ! :oops:

    Avatar
    Sembee
    Member
    #261444

    Re: Several Transport Hub servers

    What do you mean by clients?
    MX records are only used by other DNS servers. They will do a lookup on your domain for the record. If they are unable to connect, then they will use the next server listed. You don’t have to do anything for that to happen.

    Having three identical A records with different IP addresses isn’t really a recommended solution. It can be done, and a number of major email providers do work in that way. However it can provide inconsistent results, particularly during an outage. Therefore the preferred method is three unique host names, all listed in the MX records with the same cost.

    You are trying to make this more complicated than it needs to be.

    Simon.

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