Is It Time To Start Sending Your Emails Using a Subdomain?

Domain versus subdomain. What’s the difference? Why should I set up a subdomain if I am already using my company’s top-level domain? Are there any benefits to using a subdomain?

A domain is a unique name that identifies a website (, while a subdomain is an extension of the domain name that can direct within the hosting account (

If you’re on the fence, or really just want to learn more about this hot topic, you’re not alone. We have received a lot of questions about domains and subdomains lately, and many want to know why subdomains always win. For starters, subdomains have the potential to boost your overall email reputation.


When it comes to email deliverability, reputation is everything. Sorry to say it folks, reputation did not die when you graduated high school. In fact, your domain and subdomain play a big part in reputation, and this is a deciding factor when it comes to ISPs determining where the email will land (inbox, junk, promotions, etc.).

Let’s create a hypothetical scenario. Your sales team lives by the term “quantity over quality”, and even worse, they may be purchasing lists. You know that to cultivate any relationship with your subscribers, you need to first obtain their permission to send emails and then grow the relationship from there. But, how do you expect to grow a relationship if you can’t even reach the inbox because your domain has been blacklisted due to bad internal practices? Think about it, would you want another department’s emails dictating whether your emails land in the inbox or not?

This is where a subdomain will be your saving grace because other departments’ sending practices will no longer affect your sending infrastructure, due to subdomains having separate reputations. And, over time, your subscribers, and their ISPs will begin to recognize and trust your sending subdomain.

Authentication Policies

One of the four basic steps to the inbox is authentication. Your SPF and DKIM need to be set up properly and they need to be passing. ISPs, with Gmail and Microsoft leading the way, are giving increasing weight to the presence of DMARC when calculating a sender’s reputation.

By moving towards a subdomain, you can set specific authentication policies. Simply put, this means that you can set your own policy for DMARC and focus on strict alignment. Remember, your envelope-from, sending domain, and DKIM domain must all match for strict alignment, otherwise you will look suspicious to ISPs.


Using a subdomain rather than your company’s top-level domain will provide easier reputation tracking because it will be separate from other domains and subdomains being used within your company. This is extremely important in email deliverability because this allows you to gauge how many clicks, opens, forwards, etc. there were for a specific campaign. From this vital information, you can continue to tweak and update future campaigns to further increase overall email success.

Keep Calm & Email On

keep calm and email onUsing a top-level domain could be detrimental to your company’s overall productivity. Say for instance one of your emails was sent out with a broken link, which landed your top-level domain on a blacklist, and now all of your company’s emails are bouncing. Your domain cannot send emails (including corporate emails) due to that incident. This will cause quite a headache for your IT team…and the rest of your company.

So, the next time you and your team are strategizing about whether a subdomain is best for your sending infrastructure, just remember, by using a subdomain, you control your reputation, along with authentication policies. And, by using a subdomain, tracking becomes a lot easier.

Questions that Marketo folks struggle with:

Should they purchase a dedicated IP to build out the subdomain’s reputation even if they are small?

A dedicated IP for a low-volume sender could actually hurt someone’s deliverability as they will never be able to establish a reputation. I normally recommend around 500,000 sends per month to have a dedicated IP.

I do have 1 client on Marketo that sends out 100,000 emails a month (all B2B) on a dedicated IP. The only reason is that they are an international sender and the majority of the networks they send to required a dedicated IP to whitelist.

Agree on the subdomain reputation too. Gmail/Google Apps, along with others are now looking at the subdomain to determine reputation. Each mail stream and sending platform should use a different subdomain when sending out email or else you could “cross contaminate” the reputation.

When it comes to using a third party like Marketo on a shared server, how do we get affected if someone else on the same server has bad email practices?

Shared IP pools can be problematic if not managed properly. If you have a client on a shared IP pool, other senders on that pool will affect your deliverability. If a sender on the shared IP pool land on a blacklist, that affects all others on that pool. Not to mention if an ISP or network blocks the IP, mail traffic is affected for all senders. Keeping an eye out for blocks, soft bounces, blacklists, etc. can help catch these issues quicker.

It is very important to ask any email service provider about the other senders on the shared IP pool, like:

  • How many other senders are on the shared IP pool?
  • What is the typical daily, monthly volume on the shared IP pool?
  • How many IPs are in the shared IP pool?
  • What categories or lines of business comprise the shared IP pool?

For more information about becoming an email mastermind, reach out to us at

Your marketing technology experts.

At Digital Pi, we use technology to connect revenue to marketing efforts. We fuse marketing strategies, processes, data and applications to make marketing technology solutions work for clients' businesses.

Learn More
Share this resource

Cookies help us keep the site running smoothly and inform some of our advertising, but if you’d like to make adjustments, you can visit our Cookie Notice page for more information.