Domain – How should I setup separate MX records for a subdomain

domainemail

Let's say I have a domain that I run a web application on, for example cranketywidgets.com, and I'm using Google Apps for handling email for people working on that domain, for example, support@ cranketywidgets.com, jane@cranketywidgets.com, joe@cranketywidgets.com and so on.

Google's own mail services aren't always the best for sending automated reminder emails, comment notifications and so on, so the current solution I plan to pursue is to create a separate subdomain called mailer.cranketywidgets.com, run a mail server off it, and create a few accounts specifically for sending these kinds of emails.

What should the MX records and A records look like here for this?

I'm somewhat confused by the fact that MX records can be names, but that they must eventually resolve to an A record. What should the records look like here?

cranketywidgets.com – A record to actual server like 10.24.233.214

cranketywidgets.com – MX records for Google's email applications

mailer.cranketywidgets.com – MX name pointing to server's IP address

I would greatly appeciate some help on this – the answer seems like it'll be obvious, but email spam is a difficult problem to solve.

Best Answer

You should never point your MX to a IP address to be RFC compliant. Make an A record for the IP address instead and point the MX record to it.

Then the zone should look like this,

    @               IN      MX      1       ASPMX.L.GOOGLE.COM.
    @               IN      MX      5       ALT1.ASPMX.L.GOOGLE.COM.
    @               IN      MX      5       ALT2.ASPMX.L.GOOGLE.COM.
    @               IN      MX      10      ASPMX2.GOOGLEMAIL.COM.
    @               IN      MX      10      ASPMX3.GOOGLEMAIL.COM.
    @               IN      MX      10      ASPMX4.GOOGLEMAIL.COM.
    @               IN      MX      10      ASPMX5.GOOGLEMAIL.COM.
    @               IN      A       10.24.233.214
    mailer          IN      A       10.24.233.214
    mailer          IN      MX      10      mailer.cranketywidgets.com.
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