Custom Sending Domains: A Necessity or a Choice for Email Deliverability?

Question:

How to configure custom sending domains for email deliverability?

I am a sysadmin with extensive experience in email technologies such as SPF, DKIM, and DMARC. I have noticed that some email service providers (e.g., Mailchimp) require their customers to use custom sending domains (e.g., mail.customer.com) with proper DNS records to send emails on their behalf. I wonder why this is necessary, and what are the benefits and drawbacks of this approach.

I have a client who sends about 3-4k emails per day from their platform, using the traditional method of sending emails from [email protected], with reply-to addresses specific to each of their customers. I am concerned about the email deliverability and reputation of my client, especially since Gmail and Yahoo have recently tightened their security policies and started enforcing DMARC for incoming emails.

I have done some research and found out that DMARC can cause issues with reply-to headers, as it may flag them as spam or phishing attempts. This seems to be the reason why Mailchimp and others recommend using custom sending domains, as they allow for better alignment and authentication of the sender’s identity.

However, I am not sure if this is the best solution for my client, as it may involve additional costs and complexity. I also wonder if this requirement applies only to senders who exceed a certain threshold of emails to Gmail or Yahoo per day, which may not be the case for my client.

I would appreciate any expert advice or feedback on this topic. Thank you for your time and attention.

Answer:

Email deliverability is the ability of an email sender to reach the inbox of the intended recipients without being blocked, bounced, or marked as spam. Email deliverability depends on various factors, such as the sender’s reputation, the content and design of the email, the authentication and alignment of the sender’s identity, and the compliance with the policies and standards of the email service providers (ESPs).

One of the most important standards for email deliverability is DMARC, which stands for Domain-based Message Authentication, Reporting, and Conformance. DMARC is a protocol that allows email senders to specify how ESPs should handle emails that fail to pass the authentication checks of SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). SPF and DKIM are mechanisms that verify that the email sender is authorized to use the domain name in the email header.

DMARC helps to prevent email spoofing, phishing, and fraud by ensuring that only legitimate senders can use a domain name to send emails. DMARC also provides feedback reports to the email senders, which can help them to monitor and improve their email deliverability.

However, DMARC also poses some challenges for email senders who send emails on behalf of their customers, such as marketing platforms, CRM systems, or SaaS applications. These email senders typically use their own domain name (e.g., mailchimp.com) in the email header, but set the reply-to address to the customer’s domain name (e.g., [email protected]). This way, the recipients can reply directly to the customer, instead of the email sender.

The problem with this approach is that it creates a misalignment between the domain name in the email header and the domain name in the reply-to address. This misalignment can trigger the DMARC policy of the ESPs, especially Gmail and Yahoo, which have recently tightened their security measures and started enforcing DMARC for incoming emails. If the ESPs detect a misalignment, they may reject, quarantine, or mark as spam the emails that fail the DMARC check.

To avoid this issue, some email senders, such as Mailchimp, require their customers to use custom sending domains (e.g., mail.customer.com) with proper DNS records to send emails on their behalf. By using custom sending domains, the email senders can achieve alignment and authentication of the sender’s identity, as well as comply with the DMARC policy of the ESPs. This can improve the email deliverability and reputation of the email senders and their customers.

However, using custom sending domains also has some drawbacks and limitations. First, it requires the customers to set up and maintain their own DNS records, such as SPF, DKIM, and DMARC, for their custom sending domains. This can be a complex and time-consuming process, especially for customers who are not familiar with email technologies. Second, it may incur additional costs for the customers, as they may need to purchase and renew their custom sending domains, as well as pay for the email sending service. Third, it may not be necessary for all customers, as the DMARC policy of the ESPs may only apply to senders who exceed a certain threshold of emails to Gmail or Yahoo per day, which may not be the case for some customers.

Therefore, the decision to use custom sending domains for email deliverability depends on the specific needs and preferences of the email senders and their customers. There is no one-size-fits-all solution, as different email senders and customers may have different goals, challenges, and resources. The best practice is to consult with an expert or a trusted email service provider, who can provide guidance and support on how to configure custom sending domains for email deliverability.

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