Hello,

We are planning to setup a Email server with High Availability for email services so that if SMTP/POP/IMAP goes down on one server, the services switch to second server.
We are planning to use a Linux machines from a hosting provider and will do it using DNS with multiple MX records with round robin.

Now i have couple of queries regarding this setup :-

• Is this possible to have a same domain name to bind with 2 IPs i.e xyz.com point to 1.1.1.1 on one server and xyz.com point to 2.2.2.2 on second server.
• How can we setup MX records for each server on DNS for email failover.
• As we have a separate servers for this setup that means data related to email would be reside on separate server (because they have separate HDD), so in case 1st server goes down and it switch to second server, will i skipped my email which was received on 1st server before it goes down as my email client will receive them on certain period of time.

Please let me know if above is a valid query.

Simple answer is yes but if one of those IP's becomes unavailable then half the traffic will not be able to connect.

A better option would be to use HSRP between the 2 servers instead of round robin DNS.

Look at the MX records in DNS. They have a Preference value that you set. This tell the SMTP which server to connect to first and when it is down what the next server to try is.

Another thing to look into is a NAS or SAN for your email backend storage. That way when one server goes down your mails will still be available on the second server. If that is not an option then maybe look at doing an Rsync between the 2 servers to keep both up to date.

Disclaimer: I am not a email admin so there may be better options for you. The above is all off the top of my head.

Hello,

Thanks for your prompt reply and details.
However if have to do it with Cpanel/WHM, i think HSRP will not be possible as this will totally depend on hosting provider.

In case we setup a email service using Cpanel/WHM we have a specific choice to setup a Fail over services for Email.

Again the 2 biggest things you need to worry about are DATA and DNS. As long as both servers can sync their data between themselves or use a back end server you should be good there. DNS you just need to ensure you have the preference value setup. User would have to be warned that if server A isn't working use server B.

You could always talk to the provider and find out if HSRP is available or not.

Sure robert, will check with hosting provider if he provide this kind of services.
Thanks.

Do you mean that the Cpanel is hosted on third party vendor? Or you manage your own email server?

Yes, CPanel/WHM is hosted on 3rd party vendor.

Hi Robert,
HSRP is not option provided by the vendor but they will provide HA with syncing the data between the servers.

It's good that you get your data synced but you still have the problem when one server goes off line.
What are your TTL's for your DNS records?

I think it is set to 14400

That's a 4 hour setting. So someone who get this record will not ask for a new one until 4 hours have passed. If someone requests the ip address of your site 5 minutes before the server goes off line they will not get the updated information for 3+ hours. This is why a floating ip address is the way to go.