Failover ISP and email delivery

Client has a failover device where when one Internet connection goes down, it flips to the other, and back again when available.

Client wants email to be delivered to in-house server regardless of which connection he's on.

Can I just add a few MX records in the DNS for the secondary connection's IP address? Or will that screw with email flow? Reply if you've done this before.
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

John EastonDirectorCommented:
I assume here the client has two independent lines to his internal server - i.e. a leased line and ADSL backup or something similar.

I so, then setting up two MX records will do what you want.  If both connections are equal - i.e. two ADSL or two equal speed leased lines, then the MX priority can be the same.  If one is a backup give it a higher priority (i.e. first one priority 10, backup 20 etc).

One catch to watch out for is outgoing mail.  If you have an SPF record make sure both IPs are listed, otherwise mail sent from the backup could be marked as spam (as it is not being sent from your 'official' IP address).

Finally, please note some misconfigured e-mail servers could use the backup MX even when the main connection is up again, and indeed some may ignore the primary connection once it has gone down - even once it is backup again - as they can cache IP address.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Elixir2Author Commented:
Very complete answer! Thank you.

In answer to the part I left unclear, he's actually using a Cradlepoint which has a WAN connection to Time Warner Cable (which drops 2-3 times per week) and the failover is a Verizon LTE modem. Client is in a unique location with only these options.

I especially appreciate your reminder about the SPF record, as we have already seen the spam-bounce on outgoing Verizon emails.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.