When we talk about performance in email marketing, we often mention the open rate, deliverability, or even the sender reputation. But a technical parameter, often underestimated, can have a decisive impact on all these aspects: the choice of using a subdomain for email sending. Smart technical practice or strategic misstep? Let’s explore this question in the light of the real stakes of email marketing.
Sending subdomain: what exactly are we talking about?
Before making a decision, let’s set the scene. When a brand sends emails, the sender address generally follows this format: contact@company.com or news@newsletter.company.com.
In the first case, the emails are sent directly from the main domain (brand.com).
In the second, the emails are sent via a specially created subdomain (newsletter.brand.com) for email campaigns.
This choice is not just aesthetic or organizational. It affects the domain reputation, deliverability performance, email flow management, technical configuration, and even user experience.
Why do professionals opt for a dedicated subdomain?
Separate flows to better manage reputation
The main advantage of a subdomain is that it allows you to isolate the reputation of marketing emails from that of transactional emails (invoices, notifications, passwords, etc.).
Imagine, for example, that you send very frequent promotions and one of your marketing emails is marked as spam. If you use the main domain, your entire email communication can be affected, including critical messages. With a subdomain, only the latter will be sanctioned.
Optimize deliverability
ISPs evaluate a domain’s reputation to decide whether your messages should land in the inbox, promotions, or spam. Using a subdomain allows you to build a distinct reputation and, in many cases, improve the deliverability of marketing campaigns, provided its management is well handled.
Facilitate security configurations
Configuring SPF, DKIM, and DMARC on a dedicated subdomain allows better control over the authentication of sent emails, without impacting the rest of the domain. This limits the risk of configuration conflicts between different internal services (email marketing, customer support, billing system, etc.).
Subdomain or main domain: the drawbacks to know
A subdomain is not a loophole
Some marketers hope to circumvent a bad reputation by changing the subdomain. Nice try, but no! In reality, ISPs also analyze the root domain (main domain) and even the sending IP addresses.
In other words, if you use a subdomain to send unsolicited or low-quality campaigns, your main domain’s reputation could still be affected.
A subdomain does not protect against a poor strategy; it simply limits the technical consequences.
Technical resources required
Creating a subdomain involves a proper DNS setup, implementation of authentication protocols, active reputation monitoring, and rigorous management practices.
For organizations lacking technical skills, this can pose an obstacle or generate errors with unfortunate consequences.
Risk of confusion on the user side
A sender using a subdomain unknown to the recipient, for example, “mail.brand.com” instead of “brand.com,” can generate distrust. The perceived brand consistency through the email address is essential. In some cases, a poorly chosen subdomain can harm perceived credibility.
When is it a good idea to use a subdomain?
You send large volumes of emails each month
When you send thousands, or even millions of emails per week or month, the risks of complaints, bounces, or blacklisting increase significantly. In this context, using a subdomain allows you to isolate the reputation of these marketing campaigns from that of your critical emails (transactional, administrative…).
This prevents a performance drop or a one-time error (like a broken link, poor segmentation, or an aggressive message) from affecting the reputation of your entire main domain.
You manage different types of emails
Email marketing, transactional emails, relational messages, internal newsletters, etc. Each email has its own pace, tone, and audience.
Using a subdomain for each of these flows allows you to:
- Separate metrics and reputation specific to each channel;
- Adjust send frequencies independently;
- Configure specific DKIM signatures if necessary.
For example:
transaction.myshop.com for invoices and confirmations;
newsletter.myshop.com for monthly news sendings;
support.myshop.com for customer exchanges.
You use a third-party emailing platform
Tools like Mailchimp, Klaviyo, or ActiveCampaign offer the ability to customize the sending domain. Instead of sending your campaigns from a generic domain such as “@mailchimpapp.net,” you can (and should) configure a personalized subdomain, like “email.mysite.com.”
This allows for authenticating sends via your own domain, which inspires more trust among ISPs and recipients. It’s also a good way to maintain brand consistency while benefiting from the platform’s technical infrastructure.
You need fine segmentation by brand, country, or service
In a multi-brand or international group, or in a company comprising many entities, communications often need to be differentiated.
You can use a subdomain per:
- Brand: email.brandA.com, email.brandB.com;
- Country: fr.mysite.com, us.mysite.com;
- Department: recruitment.mysite.com, support.mysite.com.
This facilitates campaign management, improves traceability, and allows precise control over the performance and reputation of each entity.
Best practices to take advantage of a subdomain
Properly authenticate your subdomain: Configure SPF, DKIM, and DMARC for this subdomain and regularly monitor DMARC reports to detect any abuse or loopholes.
Proceed gradually: Do not send everything at once. Start with small volumes to engaged segments to establish a healthy reputation.
Choose a clear name: Prefer explicit subdomains (e.g., email.brand.com, info.brand.com, news.brand.com) to avoid suspicion.
Continue to adopt good sending practices: The subdomain should not be an excuse for misuse. Segment your lists, offer relevant content, respect consents, and clean your databases.
So, a smart concept or a strategic misstep?
The answer is: a smart concept… provided it is used well. A subdomain is a powerful technical tool to secure your email reputation, optimize deliverability, and effectively segment your sending flows. However, it does not replace a rigorous email strategy nor exemplary management of your lists and contents.
