Email Redundancy in Exchange (Cloud, Relay, and Multiple MX Records)

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Many small and medium businesses do not have any email redundancy, and in today’s IT environment that is unacceptable. There is 3 widely used methods for never missing or having downtime for email. Depending on the size of your business there are some that make more sense than others.

Business Solutions

  • Cloud Email – You can host your email off-site. Recommended Vendors. or Pros: Disaster prevention, Archiving, Spam filtering, and Automated Backups. Cons: Expensive (Around $15 to $25 per mailbox with all features listed above), and you can have latency issues on a bad internet connection.
  • Email Relay – Email is delivered and filter by 3rd party. Recommended Vendors. Pros: Spam Filtering, Archiving, and Spooling (Should your SMTP server go offline, it saves incoming messages and delivers them to you once it comes back online.) Cons: Cost ($5 to $10 per mailbox). Backups and Hosting are maintained On-Site. You will have an outage period where you can’t access email if your SMTP Server’s Internet goes out.
  • Multiple MX Records – Email is delivered to your server(s) via multiple internet connections. Pros: No Downtime and easy to setup Cons: Everything In-House (Depending on your in-house IT staff this could be a pro) and Extra Internet Line Cost (Business DSL $50 per month, but it is nice having redundant internet as well).

Here are my recommendations:

Business Size (<5) Cloud Computing Business Size (<20) Email Relaying *Note: This is for a business with an existing SMTP server. If your business is new or about to migrate to new systems, I'd suggest Cloud. Business Size (20+) Multiple MX Records Setting up Multiple MX Records

  • Document your 2 Internet Addresses
  • Setup the MX records for your IP Address with your Registrar. I use and here is an example for them.

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  • Setup your firewall to forward both WANs Port 25 (SMTP Port) to your private IP (SMTP Server IP) Note: You need a business grade router that has multiple WAN ports and supports Port Forwarding of port 25 on multiple WAN Ports. I’ve personally setup Draytec’s Vigor 3300 and many Sonicwall appliances that also have this capability.