How do mx records work when there are multiple ones at the same priority?

Question

I've setup my domain to work with Google apps so I've added the 5 mx records it needs to work. However, I added another mx record to work with another 3rd party service.

priority - mail server

• 1 Google Primary
• 1 3rd Party Service
• 5 Google Backup 1
• 5 Google Backup 2
• 10 Google Backup 3
• 10 Google Backup 4

The question is, how will the setup work? My objective is 2 emails delivered one to google's primary and one to the 3rd party service.

I believe with this setup a round robin scheme is used. So any incoming mail will be randomly passed to Google Primary or 3rd Party Service, if one fails it will try the other and then go down to the next priority until one of them succeeds. Is this correct?

If so, is there any way to do so?

The reason I would like such a setup is because I want my address to be omar@domain.com and want the app to receive emails directly app@domain.com. One solution is to add a separate subdomain such as as omar@mail.domain.com and have the google mx record be for that subdomain and keep the 3rd party mx record for domain.com. But it isn't pretty.

Thanks!

Answer 1

You have a bunch of different questions in your post so I'll try to answer the one in your subject...

Any MX record with the same weight will be used in a round-robin scheme. It is really up to the client to choose which one to send to as the DNS server will simply return all of the MX records for the domain and then try them based on priority.

You should try to break out your question into smaller questions as the Q&A format is only good for specific questions or problems, not over-reaching broad ideas and theories.

Good luck & welcome to ServerFault!

Answer 2

What you are trying to do cannot be done solely with MX records. You need an MTA that either sends a copy of every message to both providers or act upon them in different ways via filters.

Within Google Mail you can create filters which allow you to forward messages that follow a certain pattern (like everything sent to app@domain). It's all under the Filter tab within Settings.

Answer 3

Ideally, yes omar@domain would go to google and app@domain would go to 3rd party. But I don't think this can be done.

This would need to be done by the mail server itself. You'd direct all mail to a mail server configured to relay omar@domain to google's server, and relay app@domain to the other server. That's quite a legitimate way to configure a mail server by the way.

Presumably Google apps can even do this itself - relay app@domain to a different mail server but deliver omar@domain the normal way.