Email Deliverability

Beyond Mere Compliance: Reaching Subscriber Inboxes Through Adoption of Best Practices

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If working with email marketers has taught us at Validity anything, it’s that scrambling to maintain deliverability and adhere to the latest industry requirements is stressful!

After the EU announced The General Data Protection Regulation (GDPR) in 2016, brands could no longer rely on soft opt-in or soft opt-out approaches when collecting data.

In 2021, Apple’s Mail Privacy Protection (MPP) forced marketers to go beyond open data to understand email engagement.

And in 2024, Gmail and Yahoo’s bulk sender requirements meant that many senders had to implement well-established best practices to reach subscriber inboxes.

These examples have one thing in common: they effectively codified best practices. Before we dive deeper, let’s do a quick review of Google and Yahoo’s new requirements:

  1. DMARC adoption. Senders must publish a DMARC record with a minimum policy of p=none. They must also ensure alignment with their SPF/DKIM domains.
  2. Implementing one-click list unsubscribe. Senders must implement List-Unsubscribe-Post header as described by RFC8058 and honor all unsubscribe requests within two days.
  3. Maintaining a spam complaint rate below 0.30%. Senders must maintain their spam complaint rate threshold below 0.30 percent, though ideally, less than 0.10 percent.

“Yahoogle” compliance isn’t a magic ticket to the inbox. Many senders have checked all three requirement boxes and found themselves continuing to land in the spam folder—and we’re not surprised.

Frankly, these requirements represent the bare minimum of best practice adoption. In 2024, marketers must go beyond mere compliance to achieve successful delivery and a future-proofed email program.

It’s officially time for senders to pay attention to industry standards like RFCs and M3AAWG guidance. RFC stands for “Request for Comments” and is a formal standards-track document developed in working groups. Google and Yahoo reference several lesser-known RFCs in their best practice documentation and FAQs.

Senders who have implemented the new “Big Three” requirements but still struggle to reach subscriber inboxes: this blog post is for you! After all, yesterday’s best practices will become tomorrow’s requirements.

Let’s review some key standards that, if not followed, could negatively impact your inbox placement.

Sound infrastructure configuration

It’s not the sexiest topic, but sound infrastructure configuration is essential for successful email delivery. In addition to the authentication alphabet soup (SPF, DKIM, and DMARC), senders must also ensure they have valid PTR records and ARC authentication.

  • A pointer (PTR) record resolves an IP address to a domain or hostname. This is known as a reverse DNS lookup. Senders should publish valid, non-generic (i.e., branded) PTR records for all their sending IPs. For example, IP address 111.XX.111.XX resolves to vs.
  • Authenticated Received Chain (ARC) is an email standard that validates authentication for forwarded emails. When a message is forwarded, certain email elements can be modified in transit and cause SPF or DKIM authentication to fail. ARC can help prevent this type of authentication failure. Implementing ARC helps prevent legitimate emails from being marked as spam or phishing by subscribers by confirming they’re from a trusted source.

Compliant message formatting

Message formatting standards are all about legitimacy and transparency. When reviewing your message formatting, consider:

  • Message headers: From headers should include only one email address and not be excessively large. Gmail has published guidelines pertaining to message header size. Enforcing header size requirements helps prevent spammers and scammers from impersonating legitimate senders and protects mailbox provider users.
  • Content accuracy and transparency:
    • All elements of the message header and content should be accurate and not misleading (i.e., don’t use FWD: or RE: in your subject line!), represent the brand appropriately, and sender information should be clear and visible.
    • This transparency also applies to links and images. Links within the message body should be easy to understand and recognizable. Avoid using third-party link shorteners. Mailbox providers are not fans of hidden message content.
  • The RFC5322 standard:
    • Every message should include a Message-ID, and single-instance message headers should only be present once in a single email. Some examples of single-instance message headers include Subject:, Date:, and From:.

Implementing recommended sending practices

  • Message types should be segmented by IP or DKIM domain if you’re using multiple IPs. For example, promotional messages should be sent from one IP, and account notifications should be sent from a separate IP. Combining message types onto a single IP or domain can negatively impact deliverability. Because each IP and domain has its own reputation, this type of segregation can improve inbox placement and decrease risk.
  • Messages of the same category should use the same From: email address. This helps inform the mailbox provider (and subscriber) of the nature of the message. For example, promotional messages might come from [email protected], while account notifications might come from [email protected]. On a related note, don’t combine different types of message content within one email. Promotional content and transactional content shouldn’t mix within the same message.
  • List hygiene standards apply to every email program. Whether you’re a B2C or B2B sender, you should remove invalid subscribers after the first bounce. Senders should also have a sunset policy to suppress unengaged subscribers and monitor soft bounces regularly.

Strong, confirmed consent

Confirmed opt-in (COI) is perhaps the most hotly debated business decision for senders struggling with reputation issues. Confirmed opt-in is an acquisition strategy that favors quality over quantity. It requires subscribers to confirm their interest in receiving future emails by clicking a link before being added to a list. Senders who use COI see higher subscriber engagement rates, lower spam complaint rates, improved list quality, and elevated inbox placement rates compared to senders using single opt-in (SOI). Google and Yahoo both strongly recommend COI for optimal deliverability:

Yahoo sender requirements and recommendations: “When users subscribe to your mailing list, send them an email asking them to click to confirm their opt-in. This will improve the experience for users (who won’t sign up accidentally or get signed up maliciously) and for your list (which won’t contain uninterested people, fake email addresses, or most robots).”

Google’s email sender guidelines: “Make sure recipients opt in to get messages from you. Confirm each recipient’s email address before subscribing them…If you manage mailing lists or other email subscriptions, you should send email only to people who want to get messages from you.”

Still having issues?

If you’ve applied all the best practices outlined in this post and still see your messages landing in the spam folder: