How to create sender email addresses for new subdomains in an ESP?
Matthew Whittaker
Co-founder & CTO, Suped
Published 3 May 2025
Updated 19 Aug 2025
6 min read
When you're looking to scale your email marketing or transactional communications, using a dedicated subdomain for sending is a fundamental best practice. It helps protect your main domain's reputation from potential deliverability issues, ensuring that your primary website and corporate email remain unaffected even if your marketing emails encounter a spam filter.
A common question arises: how do you actually create sender email addresses, like 'newsletter@mail.yourdomain.com' or 'support@updates.yourdomain.com', once you have a new subdomain set up with your Email Service Provider (ESP)? The process differs significantly from setting up a personal email alias through your IT department. With ESPs, the workflow is often more streamlined and self-service after the initial domain authentication.
The role of your ESP and DNS for subdomains
The first step in using a new subdomain for email sending involves delegating its authority, at least for email purposes, to your ESP. This isn't about giving them full control over your entire domain, but rather telling the internet that your ESP is authorized to send emails on behalf of that specific subdomain. This delegation happens through DNS records.
Your ESP will provide you with specific DNS records to add to your domain's DNS settings. These typically include TXT records for SPF (Sender Policy Framework) and CNAME records for DKIM (DomainKeys Identified Mail) authentication. In some cases, you might also need to set up MX (Mail Exchanger) records for the subdomain if you intend to receive inbound replies to email addresses using that subdomain.
Typical DNS records required
TXT records: For SPF authentication, which lists authorized sending servers. Your ESP will provide the specific value.
CNAME records: Often used for DKIM authentication, which adds a digital signature to your emails. Also commonly used for click and open tracking.
MX records: Only if you expect replies to your subdomain email addresses. These direct incoming mail to your ESP or your internal mail infrastructure.
Implementing these DNS changes is usually an IT or domain administrator's task. Once these records are correctly published and propagated, your subdomain is ready for authentication within your ESP. The fundamental principles of email subdomains are well-documented, providing a solid foundation for understanding this process. You can find more information about these basics on resources like the Mailgun blog.
Authenticating your new subdomain
After you've added the necessary DNS records, the next critical step is to authenticate your subdomain within your ESP. This authentication confirms to mailbox providers that your ESP is permitted to send email using your domain, which is vital for deliverability. Without proper authentication, your emails are highly likely to land in spam folders or be rejected outright.
The ESP will guide you through this authentication process, often providing a checklist of required DNS records. It typically involves verifying the TXT records for SPF and the CNAME records for DKIM. Some ESPs might offer a simplified CNAME setup that handles both authentication and tracking. Make sure all records are correctly configured and propagated before proceeding.
Before authentication
Reputation: Emails may appear unverified, leading to low trust.
Deliverability: High risk of emails being flagged as spam or rejected.
Branding: Your ESP's domain might appear in the 'via' header, affecting brand perception.
After authentication
Reputation: Establishes your subdomain as a legitimate sender, building trust.
Branding: Emails show your subdomain as the sole sender, enhancing brand consistency.
Beyond SPF and DKIM, consider implementing DMARC on your subdomain. DMARC provides reporting and policy enforcement based on SPF and DKIM authentication results, giving you visibility into your email ecosystem and protecting against spoofing. Authenticating your subdomain is a critical step in building your sending reputation on a new ESP, as highlighted by resources such as the Kickbox blog.
Creating sender identities in your ESP
Once your subdomain is successfully authenticated with your ESP, the process of creating individual sender email addresses becomes remarkably straightforward. In most ESPs, you'll navigate to a 'Senders,' 'Sending Domains,' or 'Settings' section within their platform. Here, you'll find options to add new 'From' email addresses.
The key difference from a traditional IT request for an alias is that you typically won't need your IT team to create each new sender address for you. Because the subdomain itself is already authenticated and linked to your ESP, you as the marketer or email manager can usually create multiple sender identities on that subdomain directly. For example, you can create 'sales@mail.yourdomain.com', 'support@mail.yourdomain.com', and 'marketing@mail.yourdomain.com' without further DNS changes or IT tickets.
These sender addresses within your ESP are primarily for outbound email. If you need to receive replies to these addresses, your ESP will often allow you to specify a 'Reply-To' address, which can be an actual mailbox (e.g., your customer service inbox) that's managed separately. This setup gives you flexibility to segment your email sending while centralizing inbound communication. Understanding why you use email subdomains provides further insight into these strategic decisions.
Best practices for new sender addresses
Once your new sender addresses are configured, consider a warm-up process for your new subdomain. This involves gradually increasing your sending volume over time to build a positive sender reputation with Internet Service Providers (ISPs). Rushing the process can lead to poor deliverability and your emails being sent to the spam folder.
Regularly monitor the performance of your emails sent from these new addresses. Pay attention to engagement metrics like open rates, click-through rates, and bounce rates. Also, keep an eye on your domain's blocklist status to catch any issues early. Being on an email blacklist can severely impact your deliverability. Maintaining a clean email list and avoiding spam traps are crucial for healthy sender reputation.
Finally, ensure consistency in your 'From Name' and 'From Email' to reinforce your brand identity. While you have the flexibility to create various sender addresses, ensure each one serves a clear purpose and maintains a professional image. This attention to detail contributes significantly to recipient trust and ultimately, email deliverability.
Views from the trenches
Best practices
Once a subdomain is authenticated, the ESP typically handles the creation of sender email addresses.
Marketers usually gain the freedom to create new sender aliases themselves after subdomain authentication.
Be aware that different ESPs might have slight variations in their setup processes.
Common pitfalls
Assuming IT needs to create every single sender alias for a subdomain.
Failing to publish necessary MX records for a subdomain if inbound mail (replies) is expected.
Not verifying all required DNS records (SPF, DKIM, DMARC) before attempting to send.
Expert tips
Always confirm specific DNS requirements with your chosen Email Service Provider.
Authenticate your subdomain first using the TXT or CNAME records provided by your ESP.
Once authentication is complete, most ESPs allow you to create sender aliases directly within their platform without IT intervention.
Marketer view
Marketer from Email Geeks says that if they have a newly created subdomain for their ESP, the process for creating a sender, from, or reply-to alias using that new subdomain is generally done within the ESP itself.
November 12, 2019 - Email Geeks
Expert view
Expert from Email Geeks says that in many cases, the ESP takes ownership of the subdomain's email sending, so they are responsible for managing sender addresses.
November 12, 2019 - Email Geeks
Conclusion: streamlining sender management
Creating sender email addresses for new subdomains in an ESP is a multi-step process that moves from DNS configuration and subdomain authentication to the actual creation of sender identities within your ESP. While the initial DNS setup usually requires IT involvement, the subsequent management of 'From' and 'Reply-To' addresses for that authenticated subdomain typically falls to you, the email sender.
This streamlined approach empowers marketers and communicators to manage their email identities efficiently, segmenting campaigns, and protecting their core domain's reputation. By adhering to best practices like domain warming and continuous monitoring, you can ensure your messages reach the inbox, fostering better engagement and deliverability.
