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Assume I own the domain name, I am creating a setup where I receive email sent to using Google Apps. The MX records for already point to Google's servers and it works great. Now, I have an application server where I would like to send out automated emails, such as notifications about user activity, etc. I may also use this server to send bulk emails such as newsletters (legitimately, of course). Here, I have the option to use a subdomain for all of my automated outgoing email. Perhaps I can send these emails from and set the Reply-To header to, which would then be directed to my Google account for a real person to answer.

My question is: Is there any added benefit of sending automated email from an email address with a subdomain?

Note: I have already taken measures to use SPF and DKIM to authenticate my email from the application server. I have heard that some receiving mail servers also do a reverse MX check to determine whether your email is spam. If this is true(?), I'm assuming a subdomain would be useful because I can then make a separate MX record for to point to my application server, while keeping the other MX's for on Google.

Aside from that, is there any other reason I would use a subdomain? I notice this is commonly used in email from Groupon, Southwest Airlines, Office depot, and countless other newsletter services (sometimes they use entirely different domains), and I haven't been able to figure out why.

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You do not need a MX record to send mail. – gparent Sep 7 '13 at 0:53
I understand that an MX record is not necessary to send mail, but should I worry about receiving mail servers performing a reverse MX check and finding the IP of the MX to be different from where the email was sent from? – Michael Brook Sep 7 '13 at 2:28
You don't need to write your SPF record against the MX record. You can also use IP addresses. – gparent Sep 7 '13 at 16:45
If you don't need an MX record, what happens when the machine receiving the email is not in the domain that is being addressed? – Avery Payne Mar 9 at 18:07

1 Answer 1

up vote 1 down vote accepted

My question is: Is there any added benefit of sending automated email from an email address with a subdomain?

I don't think there are many technical reasons why a subdomain is required or necessarily better for deliverability of emails.

That being said, having/using subdomains can sometimes make things easier for large organizations because:

  • As an admin, I may not have access to global resources associated with the primary domain. For example, maybe I only manage IPs/Firewalls/DNS Zones in my specific regional office/division.
  • Even if I did have access to global resources, the scope of users/systems affected by my email changes is large. Perhaps I don't want that.
  • Even though we're specifically discussing outbound deliverability here, there is still the possibility of NDRs and failed delivery generating return traffic. Depending on the volume of mail I'm sending, I may not want delivery status notifications going back through my standard inbound mail route.

Ultimately, I think it comes down to the use case here and scope of systems affected.

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