Why can't my dedicated sending subdomain receive direct human replies?

Dedicated sending domains, especially subdomains, are often configured by Email Service Providers (ESPs) using CNAME records. These CNAMEs direct the domain's Mail Exchanger (MX) records to the ESP's infrastructure, which is designed to process automated responses like bounces and complaints. This means human replies attempting to reach an address on this specific subdomain won't typically land in your personal or corporate inbox, but rather in the ESP's system.

What happens if my email's 'From' address cannot receive mail?

Using a 'From' address that cannot receive mail leads to bounced replies from recipients, creating a frustrating experience. This can negatively impact your sender reputation, making it more likely that your emails will be flagged as spam or that your domain will be added to a blocklist (or blacklist). Always ensure your 'From' address, or at least your 'Reply-To' address, is functional.

Should I use my main domain or a subdomain for email sending?

It is generally recommended to use a subdomain (e.g., mail.yourdomain.com ) for bulk or marketing email sending. This separates your sending reputation from your primary domain (used for your website and corporate email), offering a layer of protection. If issues arise with your sending reputation, they are isolated to the subdomain, preserving the integrity of your main brand.

How do MX records relate to a dedicated sending domain?

MX (Mail Exchanger) records dictate which mail server is responsible for receiving emails for a domain. For dedicated sending subdomains configured by an ESP via CNAME, the MX records often point to the ESP's servers to handle bounces. For your primary domain, MX records point to your corporate email server (e.g., Google Workspace or Microsoft 365 ) to receive human-to-human communications.

Should my dedicated sending domain be able to receive emails? - Sender reputation - Email deliverability - Knowledge base

The question of whether your dedicated sending domain should be able to receive emails is more nuanced than it appears. Many businesses set up dedicated sending domains to enhance their email deliverability and maintain a strong sender reputation, but there's often confusion about how these domains should interact with incoming mail.

The answer largely depends on how your Email Service Provider (ESP) configures the domain and the specific purpose of the email address used in the 'From' header. While dedicated sending domains are primarily designed for outbound mail, the ability to receive replies at the 'From' address is critical for communication and avoiding issues that could lead to emails landing in spam or on a blocklist (or blacklist).

The role of a dedicated sending domain

A dedicated sending domain is primarily established to provide clear authentication for your outbound emails. This involves setting up DNS records like SPF, DKIM, and DMARC, which tell receiving mail servers that your emails are legitimate and haven't been tampered with. This authentication helps build trust with inbox providers like Google and Outlook, increasing the likelihood of your messages reaching the inbox.

The main goal is to establish a strong sender reputation associated with your brand, distinct from any shared sending infrastructure. This helps isolate your email performance, preventing issues from other senders on a shared IP or domain from affecting your deliverability. Understanding DMARC, SPF, and DKIM is key to this process.

It is worth noting the difference between the 'Mail From' address (also known as the RFC 5321.From or Return-Path) and the 'From' header address (RFC 5322.From). The 'Mail From' address is typically used by ESPs to handle bounces and is often a technical address on your dedicated sending domain. The 'From' header address is what your recipients actually see. While these don't always need to identically match for optimal delivery, their relationship is important.

Why dedicated sending domains may not receive replies

The reason many ESPs (like Klaviyo) state that your dedicated sending domain cannot receive emails stems from how they configure your DNS records, specifically through CNAME records. When you set up a dedicated sending domain, you're often instructed to create CNAME records that point your subdomain (e.g., send.yourbrand.com) to their infrastructure.

This CNAME setup typically includes the MX records necessary for the ESP to process bounces and complaints directly. In essence, any mail sent to that specific subdomain is routed to your ESP's systems, not to your corporate mail server. This is efficient for handling transactional and marketing email replies (like automated bounces), but it means that a human attempting to reply directly to hello@send.yourbrand.com might receive a bounce message or their reply might simply disappear into the ESP's bounce processing system without reaching a human.

The critical rule

You should never use an email address in your 'From' header (RFC 5322.From) that cannot receive incoming emails. Doing so can lead to a poor user experience, where replies bounce, and it can negatively impact your sender reputation, making your emails more likely to be flagged as spam or get your domain added to a blocklist (or blacklist).

This configuration is common practice for bulk sending platforms to streamline bounce handling and automate email feedback loops. It's why services like AWS SES require an MX record for your 'Mail From' domain to ensure they can receive bounce and complaint notifications.

Example CNAME record for a dedicated sending subdomainDNS

Host: send.yourbrand.com
Type: CNAME
Value: your-esp-sending-domain.com

Managing replies and domain reputation

While your dedicated sending subdomain might not accept direct human replies, it's crucial that the 'From' address presented to recipients is functional and able to receive responses. This is where the 'Reply-To' header comes into play. You can specify a different email address for replies, typically one on your primary domain (e.g., help@yourbrand.com). This ensures customer engagement and prevents a poor user experience.

Strategically separating your sending domain from your primary corporate domain offers significant benefits for your overall email deliverability and sender reputation. If your dedicated sending domain encounters deliverability issues, like landing on a blocklist or experiencing high bounce rates, it helps to contain the damage. Your primary domain, used for corporate communications and website, remains unaffected.

Purpose

Primarily for email authentication and establishing sending reputation, often configured not to receive direct user replies but to process bounces via the ESP.

MX records

CNAME typically points to ESP's bounce processing, directing incoming mail away from your primary inbox. This is also why not having an MX record for your sending domain isn't necessarily bad if mail is handled by an ESP.

Purpose

Used for website, corporate email, and direct customer replies, designed to receive and manage all general email communications.

MX records

Configured to direct incoming mail to your corporate mail server (e.g., Google Workspace, Outlook). These are essential for receiving any email at all.

This isolation is a key benefit of using a dedicated subdomain for your bulk email sending. It creates a buffer between your marketing or transactional emails and your critical business communications. If a campaign goes awry and leads to spam complaints, the issue is contained to the sending subdomain, making recovery quicker and less impactful on your main brand presence.

Furthermore, using subdomains for email helps you segregate your email streams. For instance, you might use marketing.yourbrand.com for promotional emails and transactional.yourbrand.com for order confirmations. This granularity allows for more precise reputation management and easier identification of issues, ultimately boosting overall email deliverability rates.

Practical considerations for your setup

The key takeaway is to strike a balance between technical configuration and user experience. While your dedicated sending subdomain, configured with CNAMEs, might not be set up to receive direct human replies, your 'From' address must still be a valid, functioning address that recipients can reply to.

To achieve this, always use a 'Reply-To' address that directs responses to an active inbox, typically on your primary domain. This setup allows your ESP to handle bounce processing efficiently via the sending subdomain, while ensuring that actual customer replies reach your support or sales team. Following email sending best practices, including regular monitoring of your email performance, is also essential.

Regularly checking your domain's reputation for any blocklist (blacklist) appearances is also crucial. A robust email strategy involves both technical correctness in your DNS setup and practical consideration for how recipients interact with your emails. This comprehensive approach helps ensure your messages consistently reach the inbox and maintain a positive brand image, as outlined in guides for improving email deliverability.

Views from the trenches

Best practices

Always ensure the 'From' address presented to recipients is a functioning email address.

Utilize a 'Reply-To' header that directs replies to an active inbox on your main domain.

Separate transactional and marketing email streams using dedicated subdomains for each purpose.

Common pitfalls

Using a 'From' address that cannot receive mail, leading to bounced replies and a poor user experience.

Assuming your dedicated sending subdomain can receive direct replies from humans.

Failing to configure a 'Reply-To' address, leaving recipients with no valid way to respond.

Expert tips

If your ESP uses CNAMEs for your sending domain, they typically manage the MX records for bounce processing.

The 'Mail From' (RFC 5321.From) address handles bounces, while the 'From' (RFC 5322.From) is what recipients see.

Separating sending domains helps isolate reputation issues, protecting your main brand domain.

Expert view

Expert from Email Geeks says: The domains in the From and Reply-To headers do not have as strong an identity impact as the domains used in email authentication strings.

2021-09-24 - Email Geeks

Expert view

Expert from Email Geeks says: It is absolutely crucial that you do not use a 5322.From address if the domain associated with it cannot receive email.

2021-09-24 - Email Geeks

Balancing technical setup with user experience

While your dedicated sending domain's technical configuration might prevent it from receiving direct human replies, this is often by design to streamline bounce processing for your ESP. The critical point is to ensure that the 'From' address your recipients see and interact with is always capable of receiving mail.

By using a 'Reply-To' header that points to an active inbox on your main domain, you maintain effective communication with your audience while still leveraging the deliverability benefits of a dedicated sending subdomain. This strategic approach ensures both technical compliance and a positive user experience, contributing to long-term email success.