Security > Disaster Preparation & Recovery
Internet, Email & Telephones > Email & Communication Services

Secondary Mail Servers

By Lasa Information Systems Team

All email for your organisation goes to a server from where individuals can collect their mail. What happens if that server breaks down? Do emails sent to you disappear or get bounced back to the sender?

Any email service should be set up with at least one backup server.  If your main mail server should go offline for any reason, these backup servers will receive messages for your organisation until your main server is back online.

Check Yourself

If you buy your email services in from a third party organisation (such as your ISP) this should already be set up.  However, don’t take this for granted.  You can check things are set up correctly by putting your domain name (the bit after the @ in your email addresses) into the tool at MXToolbox.  This handy tool will tell you if there are any backup mail servers for your domain, and check that they are working ok.

Get Backup

If you find you don’t have any backup mail servers you should strongly consider getting some.

If you buy your email services from a third party you should ask them why they haven’t provided backup mail servers – if they can’t provide a good answer then you should consider taking your business elsewhere.

If you have your own mail server in house (for example Microsoft Exchange) you could ask your ISP if they provide a backup mail server service.  DNS Made Easy offer backup mail servers for $12.95 a year per domain.

Fixing DNS

Once you have arranged backup mail servers, you should have given a list of server names (e.g. mx1.backup.com, mx2.backup.com).  You now need to place these in your DNS record.

DNS?

The DNS record is the information computers use to communicate with your internet connected servers.  When you send an email, your mail server looks up the correct server to send the message to.  It does this by looking at the part of the email address after the @ sign - the domain.  It then looks up part of the DNS record that says which mail server handles this particular domain.

Your DNS record is usually stored by the company with whom you registered your domain name.  If in doubt, ask your web developers where the domain name is registered.

Many Domain name registrars allow you to edit your DNS record using a web-based tool.  If they do not you may need to ask them to update your DNS record for you.

There are different parts of a DNS record.  For email, we are concerned with the MX records.  MX records tell email servers to which computer mail to a given domain should be delivered.  MX means "mail exchange".

To add your backup mail servers you need to add new MX records for each one. These should be in the format:

MX 10 main.mail.domain.com
MX 20 backup1.domain.com
MX 30 backup2.domain.com

The number after MX signifies the order of preference – mail servers will first try and deliver mail to the server with the lowest number.  If that fails they try the next lowest number, and so on until mail is delivered or there are no more servers to try.

For more information see the Wikipedia entry on MX Records.

Once you have updated your DNS record it will take up to 48 hours for the backup to start working from everywhere in the world.

Setting up backup mail servers is cheap and easy, and definitely worthwhile – essential if you host your own mail server in house.

 

A note for people using third party spam filtering services

Users of these services may have been instructed to change their MX records to point to the servers of their spam filter provider. If this is the case, you should not make further changes to your MX record without first consulting them.