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What are Email Subdomains and How do They Work in Email Marketing?

Email Subdomains

If there’s something that constantly keeps email marketers on their toes, it is figuring out how to maintain a good sender reputation. Why is it so critical, you ask? Well, it is that, eventually, which determines whether their campaigns would land in their subscribers’ inboxes or not. You see, a poor sender reputation spells doom for deliverability and that in turn severely impedes the reach and visibility of your emails. 

In the 50 years (nearly) that email has been around, governments, ISPs (Internet Service Providers), and various other regulatory bodies have had sufficient time to lay down the ground rules that businesses need to abide by in order to uphold a spotless email reputation. Warming your IP effectively, following accessibility best practices, and maintaining the hygiene of your email list are some of the most talked about tenets. Today, however, we are going to call your attention to an aspect which we feel doesn’t get the spotlight enough- the significance of using email subdomains. 

But, it’d be remiss of us to dive straight into that without covering a few fundamental things first. Let’s proceed then, shall we?

Understanding Email Subdomains

Go to your inbox. Open any random email. Now click on the “from” section of the email to see the sender’s details elaborately. What do you observe? A name followed by the “@” symbol, followed by another name, right? Well, the word that comes after the @ sign is nothing but the domain name.

In most cases, the domain name is the same as that of the business and is unique to it. Now, this domain is also referred to as the “root” domain or the “parent” domain. Subdomain, then, as the name suggests, is one that is derived from the parent domain. However, emails delivered from the subdomain are treated separately by ISPs and mailbox providers.

Conceptually, subdomains are pretty much the same as what you might have noticed in the context of websites. If the URL of the home page of business “XYZ” is, then the URL of its blog page would be Here “xyz” is the parent domain and “blog”, the subdomain. Similarly, when you receive an email from, understand that it has been delivered from the root domain. But, if the sender’s address is, then the email has been sent from the subdomain “hello”. Keep in mind that there’s no restriction as such to what you can put before the @ symbol while sending emails from your subdomain. So, it can be “Kevin” or “Laura” or “Duke” or anything you wish for it to be. 

Why Should Businesses Use Subdomains?

Your email domain is essentially an indicator of who the sender of the message is. Consequently, it is what ISPs use to monitor your sending activity. As a business, you have different kinds of emails to send out: welcome emails, newsletters, marketing emails, post-purchase emails, and feedback emails, to name a few. That’s a large volume of emails, you’d agree. If you go ahead with sending them all out under one domain, you’ll be inviting the suspicion of ISPs. It’s hard to tell what benchmarks they use to deem domains as trustworthy or otherwise. That they frown upon the act of several emails hailing from a single email domain, is for sure. Once you land in the bad books of ISPs, your sender reputation suffers. And, as we discussed above, that directly translates into your deliverability going down the dumps. 

To escape this fate, thus, businesses must consider having separate subdomains in place. Ideally, you should aim to have one for every department. That way:

1. The mistake of any one department will not cause collateral damage to the others.

2. Two departments with entirely different strategies can co-exist peacefully.

Allow us to present a hypothetical scenario revolving around each of the two cases listed above.

First case:

Suppose your marketing team has overshot the daily limit of sent emails. This will impose a shadow ban on your domain. Now, if all your departments are sending their emails from the root domain, this shadow ban will bring their operations to a halt too. In this scenario, however, if the marketing department had its own subdomain, the ban would have remained confined only to it. The others would have been able to go about their affairs as usual. 

Second case:

Say you have a team each for sending welcome emails and promotional emails. And both are using the root domain. Welcome emails, on any given day, register better engagement rates than promotional ones. In fact, it wouldn’t be much of a stretch to say that the engagement levels of these two occupy opposite ends of the spectrum. So, what do you think will happen when you send out both your welcome and promotional emails from the same domain? The low engagement levels of your marketing and promotional levels will, at some stage, push ISPs to subject your domain to greater scrutiny. Ultimately, this will hamper your high-engagement welcome emails from reaching your subscribers’ inboxes too. The culprit of this unfortunate series of events is neither of these teams but the fact that they did not consider separate subdomains.

Moreover, not using subdomains can keep you from effectively measuring your performance. Think about it- will you be able to obtain a deep insight into the performance of any single category of emails if you are sending all of them through one domain? Well, you will be but it will demand more effort. Therefore, establishing distinct subdomains can be a good idea to optimizing your email strategy, thereby paving the way for improved results.

Setting up a Subdomain

Now that we’ve talked at length about the significance of email subdomains, let us take a look at how you can set up one. At the outset, let us clarify that this process varies across ESPs (Email Service Providers), so what we have done here is listed down some best practices that will hold true across all.

Few Mistakes You Should Avoid

Wrapping It Up

Improving email deliverability tops the priority list of all email marketers out there. Using email subdomains is just one among the many things that help them inch closer to it. Grasping the concept of subdomains can be a bit tricky when you are new to it. We hope the points stated above help you gain familiarity at the earliest!

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