How will Google and Yahoo's new email authentication policies affect senders using shared domains and ESP authentication?
Matthew Whittaker
Co-founder & CTO, Suped
Published 4 Aug 2025
Updated 17 Aug 2025
8 min read
The email landscape is constantly evolving, and 2024 brought significant changes with new policies from Google and Yahoo. These updates aim to enhance email security and reduce spam by enforcing stricter authentication standards. While these changes impact all senders, they have particular implications for those relying on shared domains and Email Service Provider (ESP) authentication.
For many years, email authentication protocols like SPF, DKIM, and DMARC were considered best practices, tools that helped improve deliverability but weren't strictly mandatory for all messages. However, Google and Yahoo are now turning these recommendations into hard requirements, especially for bulk senders.
This shift necessitates a re-evaluation of current sending practices, particularly for organizations utilizing shared infrastructure or those where their ESP handles most of the authentication. Understanding these policies is crucial for maintaining good inbox placement and avoiding issues like emails being rejected or sent to the spam folder.
The core of the new policies revolves around strong email authentication. This means ensuring your emails are properly signed using SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance). These protocols work together to verify that an email sender is legitimate and authorized to send mail on behalf of a domain. Without them, emails are more likely to be flagged as suspicious.
A key aspect of these requirements is DMARC alignment. This means the domain in your email's From: header (the visible sender) must align with the domain used for either SPF or DKIM authentication. Traditionally, many senders, particularly smaller ones or those just starting out, have relied on their ESP's shared domain for authentication. This practice often results in a via tag next to the sender's name in recipient inboxes, indicating that the email was sent via another domain. These changes are designed to eliminate that.
For bulk senders, defined by Google as sending over 5,000 emails per day to Gmail addresses, the requirements are even stricter, including a mandatory DMARC policy with a minimum of p=none, and a low spam rate threshold. The overall goal is to make email safer and more trustworthy for recipients.
Key authentication protocols
SPF: Verifies authorized sending IPs for your domain. It prevents spammers from sending emails that appear to originate from your domain.
DKIM: Adds a digital signature to your emails, ensuring the content hasn't been tampered with in transit. This signature is tied to your domain.
DMARC: Builds on SPF and DKIM, allowing domain owners to specify how receiving servers should handle emails that fail authentication and to receive reports on email authentication failures. You can learn more about this by checking out a simple guide to DMARC, SPF, and DKIM.
The impact of shared domains and ESP authentication
The new policies directly impact senders using shared domains offered by their ESP. When you send emails through an ESP without setting up custom domain authentication, your emails are typically signed by the ESP's domain, not yours. This creates a disconnect between the From: header domain and the authenticated domain, leading to DMARC alignment failure.
ESPs like Klaviyo and ActiveCampaign often have default DKIM authentication on their shared internal domains. While this offers a baseline of security, it doesn't meet the new alignment requirements if senders continue to use their own From: domain without custom authentication. This is particularly important because shared sender reputation can lead to deliverability problems.
The consequence for non-compliance is likely to be increased email rejection or delivery to the spam folder. To avoid this, senders must prioritize setting up their own dedicated domain authentication within their ESP, ensuring that their From: domain is fully authenticated and aligned. You can read more about how shared IP pools and sending domains impact reputation.
Shared domain sending
Authentication: Emails are authenticated using the ESP's domain, not the sender's.
Visibility: Often results in a via tag or similar indicator in recipient inboxes.
Reputation: Sender reputation is tied to the shared domain, making it vulnerable to other users' poor sending practices. This affects email deliverability and domain reputation.
Compliance risk: High risk of non-compliance with new Google/Yahoo policies, leading to spam folder delivery or rejection.
Branded domain sending
Authentication: Emails are authenticated using the sender's own domain, ensuring DMARC alignment.
Visibility: The email appears to come directly from the sender's domain, building brand trust.
Reputation: Sender reputation is built on the dedicated domain, giving the sender full control and isolating them from other ESP users.
Compliance: Meets all new authentication requirements, leading to better inbox placement and deliverability.
Interpreting 'recommendations' as requirements
When Google or Yahoo state, "We recommend you always use the same domain for email authentication and hosting your public website. Turn on DKIM for the domain that sends your email," it's a strong indicator of a future mandate rather than a mere suggestion. In the world of email deliverability, a "recommendation" from major mailbox providers often carries the weight of a requirement. Non-compliance, especially for bulk senders, will likely lead to severe deliverability penalties.
The message is clear: senders should own their sending domain and use it for DKIM signing. While it's technically possible to have multiple DKIM signatures on a message, one of them should be an aligned signature from your own domain. If you're a high-volume sender, this is non-negotiable. Learn more about how the Google and Yahoo changes impact email marketers.
This also means a definitive end to using free email domains (e.g., @gmail.com or @yahoo.com) in the From: header when sending marketing or transactional emails via an ESP. Mailbox providers prioritize their users' experience, and a lack of proper authentication makes it harder for them to filter out spam and phishing attempts. Consequently, non-compliant senders will face diminished inbox placement, even if their volume is not high.
To ensure continued deliverability, all senders should implement strong authentication for their own domains. This involves: setting up SPF, DKIM, and DMARC records in your domain's DNS. While your ESP might handle some of the technical setup, it's your responsibility to configure these records for your specific domain.
For bulk senders, it is now mandatory to publish a DMARC record. Even a p=none policy, which monitors but doesn't block emails failing DMARC, is sufficient to meet the initial requirement. This allows you to gather important data on your email streams and gradually move to stricter policies like p=quarantine or p=reject as your configuration matures. You can find out more about whether Yahoo and Gmail require DMARC.
It's also crucial to monitor your spam rate, keeping it below the 0.3% threshold. This requires clean mailing lists and engaging content. A high spam rate can quickly land your domain on a blocklist (or blacklist), severely impacting your ability to reach the inbox. Understanding what happens when your domain is on a blacklist is important.
Your ESP plays a critical role here. They should be actively updating their platforms to help senders comply. Many ESPs, including major ones, are already implementing changes to facilitate dedicated domain authentication and enforce new policies. Make sure your ESP provides clear guidance and support for setting up your own aligned SPF, DKIM, and DMARC records. For senders using multiple ESPs, it's essential to understand how to set up email authentication for multiple ESPs on the same domain.
Requirement
Action for senders
Affected senders
SPF & DKIM authentication
Configure SPF and DKIM records for your sending domain in your DNS.
All senders
DMARC record
Publish a DMARC record (even p=none) for your sending domain.
Bulk senders (>5,000 emails/day)
DMARC alignment
Ensure your From: domain aligns with your SPF or DKIM authenticated domain.
Bulk senders (highly recommended for all)
Low spam rate
Maintain a spam rate below 0.3% to avoid negative reputation impacts.
All senders (monitored for bulk senders)
Branded sending domain
Avoid using free email domains (like gmail.com) as your From: address when sending via an ESP.
All senders (critical for bulk)
Views from the trenches
Best practices
Always use a domain you own for DKIM signing to ensure proper authentication.
Implement DMARC with aligned SPF or DKIM, ideally both, for optimal deliverability.
For ESPs, use their dedicated DKIM setup option to align your sending domain.
Common pitfalls
Relying solely on shared ESP domains for authentication, leading to DMARC misalignment.
Using free email domains (e.g., @gmail.com) in the From header when sending via an ESP.
Underestimating Google and Yahoo's 'recommendations' as mere suggestions, risking deliverability.
Expert tips
If sending less than 5000 emails per day, you might experience temporary leniency, but prepare for future stricter enforcement.
Even if your emails currently deliver fine with shared authentication, the industry is moving towards stricter norms, so adapt early.
Ensure your ESP is actively updating their infrastructure to support the new requirements for their customers.
Expert view
Expert from Email Geeks says: Senders should own a domain and use it to DKIM sign their messages.
2023-10-25 - Email Geeks
Expert view
Expert from Email Geeks says: When Google and Yahoo state something as a 'recommendation,' it carries the weight of a requirement in terms of deliverability.
2023-10-25 - Email Geeks
Adapting to evolving email standards
The new email authentication policies from Google and Yahoo mark a significant step towards a more secure and trustworthy email ecosystem. For senders, this means moving beyond basic shared ESP authentication and embracing full, dedicated domain authentication with aligned SPF, DKIM, and DMARC.
While this may seem like a hurdle, it ultimately benefits legitimate senders by improving inbox placement and protecting brand reputation. Proactive adoption of these standards will ensure your emails continue to reach their intended recipients without being caught in spam filters or blocklists (or blacklists).
The industry is collectively moving in this direction, and those who adapt will thrive. Those who resist risk being left behind, with their emails increasingly failing to deliver. Embrace these changes as an opportunity to strengthen your email program and build greater trust with your audience. If you're experiencing delivery issues, consider reviewing why your emails are going to spam.
Klaviyo and 
ActiveCampaign often have default DKIM authentication on their shared internal domains. While this offers a baseline of security, it doesn't meet the new alignment requirements if senders continue to use their own From: domain without custom authentication. This is particularly important because shared sender reputation can lead to deliverability problems.
gmail.com) as your From: address when sending via an ESP.
