multiple MX records for a single 2010 exchange server

Posted on 2012-09-20
Last Modified: 2012-09-21
What is the best way to configure 2 MX records, DNS, on a single exchange 2010 server with two separate internet providers so that when one line out fails I am still able to receive mail on the other line.  Am I able to prioritize the MX records in DNS?
Question by:birddogsd
    LVL 12

    Assisted Solution

    You can create multiple MX records and set them to different priorities. However the routing part of the two ISPs is probably the trickier part. To do it at the network level you would need policy based routing. However, nite that I think about it, maybe you can create multiple send and receive connectors to use different ips?
    LVL 20

    Assisted Solution

    by:Svet Paperov
    Yes, you can set two MX to two different IP addresses. The MX record has a priority field that you need to specifies. The sening server will normaly se the MX with the lower piority value first.

    Author Comment

    So two MX records, one for each ISP and tied to one FQDN and I can set the main providers MX record priority value to the lower value and when that line goes down I can still receive mail from the other?
    LVL 12

    Expert Comment

    You will need two fqdns, one for each of the ips that you are using.
    LVL 11

    Accepted Solution

    Create two FQDN's representing the Exchange server's two public IP addresses.
    Set two MX records, each pointing to one of the FQDN's.  Priority doesn't matter, unless YOU want most of the traffic coming over 1 ISP vs the other.

    Let's call it and

    mx  10
    mx  10

    The inbound mail is easy - it's the outbound that will give you grey hair.

    In your Exchange config, tell it that the mail server name is "" - it will send a "HELO"  (it's worth checking your SMTP headers to make sure!).  when all is happy with the primary ISP, it works.  (Don't forget about a PTR record for - talk to your ISP about that, otherwise AOL and COMCAST will deny you)

    The trickier part is getting the HELO, the forward and reverse DNS right on *both* primary outbound and secondary outbound.  

    Make sure your ISP's will set a REVERSE DNS to match your HELO statement.  Even so, some mail servers will complain when they see your outbound packet is coming from the secondary ISP.  If the primary fails, the mail server 'should' sent out the secondary ISP.  

    A receiving mail server MIGHT say:  Hmm, I see this source IP address (, and a helo of  If I do a reverse DNS lookup on, it's not pointing to - therefore, this must be spam.

    The way I've gotten around that is another Send Connector in Exchange with a higher priority then the first Send Connector, routing to an on-premise SMTP relay (IIS will do fine) that says "HELO"

    There might be a more elegant way around it... anyone care to comment?
    LVL 63

    Expert Comment

    by:Simon Butler (Sembee)
    If you are using two different ISPs but email can go out via either of them, then the only way to ensure that everything works is to use an independant smart host. That isn't an ISP smart host as that will not work if the email comes out from another host.
    There are services around that can do that for you, or you can simply use a web server to bounce the email off. That way it doesn't matter how the email gets to the smart host, the smart host is doing the delivery.


    Author Closing Comment

    All excellent and correct answers.  I now have two MX records with rev DNS for each.  Both pass smtp testing.
    mx  10
    mx  20

    Featured Post

    IT, Stop Being Called Into Every Meeting

    Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

    Join & Write a Comment

    "Migrate" an SMTP relay receive connector to a new server using info from an old server.
    Local Continuous Replication is a cost effective and quick way of backing up Exchange server data. The following article describes the steps required to configure Local Continuous Replication. Also, the article tells you how to restore from a backup…
    Windows 8 comes with a dramatically different user interface known as Metro. Notably missing from the new interface is a Start button and Start Menu. Many users do not like it, much preferring the interface of earlier versions — Windows 7, Windows X…
    This video discusses moving either the default database or any database to a new volume.

    732 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    22 Experts available now in Live!

    Get 1:1 Help Now